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	$197.94	11.717%	$221.1326	$221.13	$221.15	$221.10
Purchase #2	$40.62	5.747%	$42.9544	$42.95	$42.95	$43.00
Purchase #3	$171.33	8.399%	$185.72	$185.72	$185.70	$185.70
Purchase #4	$62.77	7.193%	$67.285	$67.29	$67.30	$67.30
Purchase #5	$226.72	13.459%	$257.2342	$257.23	$257.25	$257.20
Purchase #6	$185.87	10.221%	$204.8678	$204.87	$204.85	$204.90
Purchase #7	$56.88	6.709%	$60.6961	$60.70	$60.70	$60.70
7 purchase totals =	$942.13		$1,039.8901	$1,039.89	$1,039.90	$1,039.90