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	$47.55	12.233%	$53.3668	$53.37	$53.35	$53.40
Purchase #2	$20.25	13.188%	$22.9206	$22.92	$22.90	$22.90
Purchase #3	$222.81	4.575%	$233.0036	$233.00	$233.00	$233.00
Purchase #4	$194.90	7.311%	$209.1491	$209.15	$209.15	$209.10
Purchase #5	$151.65	10.489%	$167.5566	$167.56	$167.55	$167.60
Purchase #6	$228.71	8.265%	$247.6129	$247.61	$247.60	$247.60
Purchase #7	$227.29	12.773%	$256.3218	$256.32	$256.30	$256.30
7 purchase totals =	$1,093.16		$1,189.9314	$1,189.93	$1,189.85	$1,189.90