Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.78	6.360%	$167.8148	$167.81	$167.80	$167.80
Purchase #2	$214.27	5.719%	$226.5241	$226.52	$226.50	$226.50
Purchase #3	$240.79	9.466%	$263.5832	$263.58	$263.60	$263.60
Purchase #4	$68.84	8.782%	$74.8855	$74.89	$74.90	$74.90
Purchase #5	$114.98	9.508%	$125.9123	$125.91	$125.90	$125.90
Purchase #6	$211.27	5.691%	$223.2934	$223.29	$223.30	$223.30
Purchase #7	$107.34	6.768%	$114.6048	$114.60	$114.60	$114.60
7 purchase totals =	$1,115.27		$1,196.6181	$1,196.60	$1,196.60	$1,196.60