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	$5.46	4.503%	$5.7059	$5.71	$5.70	$5.70
Purchase #2	$100.52	10.719%	$111.2947	$111.29	$111.30	$111.30
Purchase #3	$67.32	6.589%	$71.7557	$71.76	$71.75	$71.80
Purchase #4	$120.78	6.399%	$128.5087	$128.51	$128.50	$128.50
Purchase #5	$206.41	5.430%	$217.6181	$217.62	$217.60	$217.60
Purchase #6	$181.66	4.554%	$189.9328	$189.93	$189.95	$189.90
Purchase #7	$19.96	13.870%	$22.7285	$22.73	$22.75	$22.70
7 purchase totals =	$702.11		$747.5444	$747.55	$747.55	$747.50