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	$174.68	4.594%	$182.7048	$182.70	$182.70	$182.70
Purchase #2	$78.58	8.378%	$85.1634	$85.16	$85.15	$85.20
Purchase #3	$167.30	10.269%	$184.48	$184.48	$184.50	$184.50
Purchase #4	$36.45	10.120%	$40.1387	$40.14	$40.15	$40.10
Purchase #5	$30.56	6.650%	$32.5922	$32.59	$32.60	$32.60
Purchase #6	$105.82	3.409%	$109.4274	$109.43	$109.45	$109.40
Purchase #7	$14.98	5.449%	$15.7963	$15.80	$15.80	$15.80
7 purchase totals =	$608.37		$650.3028	$650.30	$650.35	$650.30