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	$125.42	6.586%	$133.6802	$133.68	$133.70	$133.70
Purchase #2	$162.37	7.434%	$174.4406	$174.44	$174.45	$174.40
Purchase #3	$232.67	9.809%	$255.4926	$255.49	$255.50	$255.50
Purchase #4	$223.72	12.307%	$251.2532	$251.25	$251.25	$251.30
Purchase #5	$154.46	7.152%	$165.507	$165.51	$165.50	$165.50
Purchase #6	$39.37	13.695%	$44.7617	$44.76	$44.75	$44.80
Purchase #7	$38.27	5.628%	$40.4238	$40.42	$40.40	$40.40
7 purchase totals =	$976.28		$1,065.5591	$1,065.55	$1,065.55	$1,065.60