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	$193.43	3.298%	$199.8093	$199.81	$199.80	$199.80
Purchase #2	$59.41	10.397%	$65.5869	$65.59	$65.60	$65.60
Purchase #3	$164.68	5.148%	$173.1577	$173.16	$173.15	$173.20
Purchase #4	$226.49	13.413%	$256.8691	$256.87	$256.85	$256.90
Purchase #5	$61.50	11.515%	$68.5817	$68.58	$68.60	$68.60
Purchase #6	$247.61	4.146%	$257.8759	$257.88	$257.90	$257.90
Purchase #7	$64.54	7.715%	$69.5193	$69.52	$69.50	$69.50
7 purchase totals =	$1,017.66		$1,091.3999	$1,091.41	$1,091.40	$1,091.50