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	$191.46	4.865%	$200.7745	$200.77	$200.75	$200.80
Purchase #2	$224.25	9.123%	$244.7083	$244.71	$244.70	$244.70
Purchase #3	$164.72	3.390%	$170.304	$170.30	$170.30	$170.30
Purchase #4	$205.58	3.521%	$212.8185	$212.82	$212.80	$212.80
Purchase #5	$68.96	4.167%	$71.8336	$71.83	$71.85	$71.80
Purchase #6	$131.69	5.638%	$139.1147	$139.11	$139.10	$139.10
Purchase #7	$19.51	12.491%	$21.947	$21.95	$21.95	$21.90
7 purchase totals =	$1,006.17		$1,061.5006	$1,061.49	$1,061.45	$1,061.40