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	$87.67	7.298%	$94.0682	$94.07	$94.05	$94.10
Purchase #2	$100.89	5.340%	$106.2775	$106.28	$106.30	$106.30
Purchase #3	$227.44	13.477%	$258.0921	$258.09	$258.10	$258.10
Purchase #4	$69.27	10.159%	$76.3071	$76.31	$76.30	$76.30
Purchase #5	$88.49	13.272%	$100.2344	$100.23	$100.25	$100.20
Purchase #6	$249.81	10.431%	$275.8677	$275.87	$275.85	$275.90
Purchase #7	$32.26	5.165%	$33.9262	$33.93	$33.95	$33.90
7 purchase totals =	$855.83		$944.7732	$944.78	$944.80	$944.80