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	$52.92	11.810%	$59.1699	$59.17	$59.15	$59.20
Purchase #2	$124.28	10.112%	$136.8472	$136.85	$136.85	$136.80
Purchase #3	$224.95	7.199%	$241.1442	$241.14	$241.15	$241.10
Purchase #4	$160.52	7.385%	$172.3744	$172.37	$172.35	$172.40
Purchase #5	$5.72	7.351%	$6.1405	$6.14	$6.15	$6.10
Purchase #6	$137.58	11.865%	$153.9039	$153.90	$153.90	$153.90
Purchase #7	$101.53	4.352%	$105.9486	$105.95	$105.95	$105.90
7 purchase totals =	$807.50		$875.5287	$875.52	$875.50	$875.40