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	$155.92	3.157%	$160.8424	$160.84	$160.85	$160.80
Purchase #2	$69.42	12.806%	$78.3099	$78.31	$78.30	$78.30
Purchase #3	$6.80	10.586%	$7.5198	$7.52	$7.50	$7.50
Purchase #4	$107.97	4.107%	$112.4043	$112.40	$112.40	$112.40
Purchase #5	$105.40	5.865%	$111.5817	$111.58	$111.60	$111.60
Purchase #6	$115.98	7.668%	$124.8733	$124.87	$124.85	$124.90
Purchase #7	$201.85	4.734%	$211.4056	$211.41	$211.40	$211.40
7 purchase totals =	$763.34		$806.9370	$806.93	$806.90	$806.90