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	$151.38	11.569%	$168.8932	$168.89	$168.90	$168.90
Purchase #2	$12.62	5.386%	$13.2997	$13.30	$13.30	$13.30
Purchase #3	$236.77	7.164%	$253.7322	$253.73	$253.75	$253.70
Purchase #4	$158.58	5.809%	$167.7919	$167.79	$167.80	$167.80
Purchase #5	$37.47	4.828%	$39.2791	$39.28	$39.30	$39.30
Purchase #6	$44.97	13.142%	$50.88	$50.88	$50.90	$50.90
Purchase #7	$38.63	10.576%	$42.7155	$42.72	$42.70	$42.70
7 purchase totals =	$680.42		$736.5916	$736.59	$736.65	$736.60