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	$115.96	7.222%	$124.3346	$124.33	$124.35	$124.30
Purchase #2	$30.55	11.816%	$34.1598	$34.16	$34.15	$34.20
Purchase #3	$236.37	4.592%	$247.2241	$247.22	$247.20	$247.20
Purchase #4	$157.29	10.840%	$174.3402	$174.34	$174.35	$174.30
Purchase #5	$141.54	3.454%	$146.4288	$146.43	$146.45	$146.40
Purchase #6	$212.29	5.650%	$224.2844	$224.28	$224.30	$224.30
Purchase #7	$98.69	13.266%	$111.7822	$111.78	$111.80	$111.80
7 purchase totals =	$992.69		$1,062.5541	$1,062.54	$1,062.60	$1,062.50