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	$148.62	7.316%	$159.493	$159.49	$159.50	$159.50
Purchase #2	$163.97	4.224%	$170.8961	$170.90	$170.90	$170.90
Purchase #3	$67.82	5.648%	$71.6505	$71.65	$71.65	$71.70
Purchase #4	$170.79	12.252%	$191.7152	$191.72	$191.70	$191.70
Purchase #5	$229.40	7.804%	$247.3024	$247.30	$247.30	$247.30
Purchase #6	$54.90	8.770%	$59.7147	$59.71	$59.70	$59.70
Purchase #7	$123.34	3.428%	$127.5681	$127.57	$127.55	$127.60
7 purchase totals =	$958.84		$1,028.3400	$1,028.34	$1,028.30	$1,028.40