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	$199.49	9.390%	$218.2221	$218.22	$218.20	$218.20
Purchase #2	$166.27	4.639%	$173.9833	$173.98	$174.00	$174.00
Purchase #3	$91.31	4.767%	$95.6627	$95.66	$95.65	$95.70
Purchase #4	$67.32	7.200%	$72.167	$72.17	$72.15	$72.20
Purchase #5	$139.48	4.195%	$145.3312	$145.33	$145.35	$145.30
Purchase #6	$38.64	10.408%	$42.6617	$42.66	$42.65	$42.70
Purchase #7	$154.82	7.689%	$166.7241	$166.72	$166.70	$166.70
7 purchase totals =	$857.33		$914.7521	$914.74	$914.70	$914.80