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	$129.55	9.374%	$141.694	$141.69	$141.70	$141.70
Purchase #2	$78.90	13.120%	$89.2517	$89.25	$89.25	$89.30
Purchase #3	$228.77	11.733%	$255.6116	$255.61	$255.60	$255.60
Purchase #4	$132.92	13.456%	$150.8057	$150.81	$150.80	$150.80
Purchase #5	$30.67	8.112%	$33.158	$33.16	$33.15	$33.20
Purchase #6	$245.80	7.227%	$263.564	$263.56	$263.55	$263.60
Purchase #7	$138.54	11.308%	$154.2061	$154.21	$154.20	$154.20
7 purchase totals =	$985.15		$1,088.2911	$1,088.29	$1,088.25	$1,088.40