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	$82.47	13.343%	$93.474	$93.47	$93.45	$93.50
Purchase #2	$12.50	13.156%	$14.1445	$14.14	$14.15	$14.10
Purchase #3	$181.65	3.565%	$188.1258	$188.13	$188.15	$188.10
Purchase #4	$36.44	10.443%	$40.2454	$40.25	$40.25	$40.20
Purchase #5	$192.61	11.672%	$215.0914	$215.09	$215.10	$215.10
Purchase #6	$37.84	8.186%	$40.9376	$40.94	$40.95	$40.90
Purchase #7	$198.47	5.575%	$209.5347	$209.53	$209.55	$209.50
7 purchase totals =	$741.98		$801.5534	$801.55	$801.60	$801.40