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	$141.28	10.300%	$155.8318	$155.83	$155.85	$155.80
Purchase #2	$158.91	7.361%	$170.6074	$170.61	$170.60	$170.60
Purchase #3	$186.77	13.835%	$212.6096	$212.61	$212.60	$212.60
Purchase #4	$133.83	5.394%	$141.0488	$141.05	$141.05	$141.00
Purchase #5	$106.71	3.587%	$110.5377	$110.54	$110.55	$110.50
Purchase #6	$93.39	6.539%	$99.4968	$99.50	$99.50	$99.50
Purchase #7	$240.76	6.425%	$256.2288	$256.23	$256.25	$256.20
7 purchase totals =	$1,061.65		$1,146.3609	$1,146.37	$1,146.40	$1,146.20