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	$33.82	10.210%	$37.273	$37.27	$37.25	$37.30
Purchase #2	$176.94	8.555%	$192.0772	$192.08	$192.10	$192.10
Purchase #3	$250.46	7.249%	$268.6158	$268.62	$268.60	$268.60
Purchase #4	$140.90	10.111%	$155.1464	$155.15	$155.15	$155.10
Purchase #5	$78.61	8.561%	$85.3398	$85.34	$85.35	$85.30
Purchase #6	$214.92	13.791%	$244.5596	$244.56	$244.55	$244.60
Purchase #7	$217.85	7.551%	$234.2999	$234.30	$234.30	$234.30
7 purchase totals =	$1,113.50		$1,217.3117	$1,217.32	$1,217.30	$1,217.30