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	$173.27	6.829%	$185.1026	$185.10	$185.10	$185.10
Purchase #2	$103.54	13.413%	$117.4278	$117.43	$117.45	$117.40
Purchase #3	$71.82	8.773%	$78.1208	$78.12	$78.10	$78.10
Purchase #4	$163.64	13.534%	$185.787	$185.79	$185.80	$185.80
Purchase #5	$32.97	9.660%	$36.1549	$36.15	$36.15	$36.20
Purchase #6	$18.58	10.539%	$20.5381	$20.54	$20.55	$20.50
Purchase #7	$107.81	3.748%	$111.8507	$111.85	$111.85	$111.90
7 purchase totals =	$671.63		$734.9819	$734.98	$735.00	$735.00