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	$223.60	10.684%	$247.4894	$247.49	$247.50	$247.50
Purchase #2	$204.28	13.504%	$231.866	$231.87	$231.85	$231.90
Purchase #3	$102.44	13.767%	$116.5429	$116.54	$116.55	$116.50
Purchase #4	$184.31	6.419%	$196.1409	$196.14	$196.15	$196.10
Purchase #5	$55.39	5.867%	$58.6397	$58.64	$58.65	$58.60
Purchase #6	$40.83	7.677%	$43.9645	$43.96	$43.95	$44.00
Purchase #7	$144.40	4.240%	$150.5226	$150.52	$150.50	$150.50
7 purchase totals =	$955.25		$1,045.1660	$1,045.16	$1,045.15	$1,045.10