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	$236.70	7.441%	$254.3128	$254.31	$254.30	$254.30
Purchase #2	$19.91	8.727%	$21.6475	$21.65	$21.65	$21.60
Purchase #3	$182.74	8.593%	$198.4428	$198.44	$198.45	$198.40
Purchase #4	$55.79	6.741%	$59.5508	$59.55	$59.55	$59.60
Purchase #5	$69.44	5.605%	$73.3321	$73.33	$73.35	$73.30
Purchase #6	$19.58	6.166%	$20.7873	$20.79	$20.80	$20.80
Purchase #7	$87.75	3.158%	$90.5211	$90.52	$90.50	$90.50
7 purchase totals =	$671.91		$718.5944	$718.59	$718.60	$718.50