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	$232.60	3.853%	$241.5621	$241.56	$241.55	$241.60
Purchase #2	$246.36	4.161%	$256.611	$256.61	$256.60	$256.60
Purchase #3	$111.57	12.166%	$125.1436	$125.14	$125.15	$125.10
Purchase #4	$83.85	8.422%	$90.9118	$90.91	$90.90	$90.90
Purchase #5	$38.25	7.302%	$41.043	$41.04	$41.05	$41.00
Purchase #6	$250.28	10.312%	$276.0889	$276.09	$276.10	$276.10
Purchase #7	$92.82	6.660%	$99.0018	$99.00	$99.00	$99.00
7 purchase totals =	$1,055.73		$1,130.3622	$1,130.35	$1,130.35	$1,130.30