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	$106.54	9.282%	$116.429	$116.43	$116.45	$116.40
Purchase #2	$155.79	8.201%	$168.5663	$168.57	$168.55	$168.60
Purchase #3	$199.77	6.224%	$212.2037	$212.20	$212.20	$212.20
Purchase #4	$132.94	11.630%	$148.4009	$148.40	$148.40	$148.40
Purchase #5	$57.72	6.263%	$61.335	$61.34	$61.35	$61.30
Purchase #6	$209.41	6.393%	$222.7976	$222.80	$222.80	$222.80
Purchase #7	$61.38	7.443%	$65.9485	$65.95	$65.95	$65.90
7 purchase totals =	$923.55		$995.6810	$995.69	$995.70	$995.60