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	$57.39	9.243%	$62.6946	$62.69	$62.70	$62.70
Purchase #2	$181.59	13.406%	$205.934	$205.93	$205.95	$205.90
Purchase #3	$52.98	4.830%	$55.5389	$55.54	$55.55	$55.50
Purchase #4	$17.64	4.750%	$18.4779	$18.48	$18.50	$18.50
Purchase #5	$229.86	6.523%	$244.8538	$244.85	$244.85	$244.90
Purchase #6	$242.96	11.743%	$271.4908	$271.49	$271.50	$271.50
Purchase #7	$132.28	4.274%	$137.9336	$137.93	$137.95	$137.90
7 purchase totals =	$914.70		$996.9236	$996.91	$997.00	$996.90