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	$93.57	5.266%	$98.4974	$98.50	$98.50	$98.50
Purchase #2	$157.79	4.771%	$165.3182	$165.32	$165.30	$165.30
Purchase #3	$244.86	4.209%	$255.1662	$255.17	$255.15	$255.20
Purchase #4	$111.75	7.856%	$120.5291	$120.53	$120.55	$120.50
Purchase #5	$176.31	11.559%	$196.6897	$196.69	$196.70	$196.70
Purchase #6	$190.49	8.256%	$206.2169	$206.22	$206.20	$206.20
Purchase #7	$198.65	12.143%	$222.7721	$222.77	$222.75	$222.80
7 purchase totals =	$1,173.42		$1,265.1896	$1,265.20	$1,265.15	$1,265.20