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	$52.66	13.762%	$59.9071	$59.91	$59.90	$59.90
Purchase #2	$112.72	11.539%	$125.7268	$125.73	$125.75	$125.70
Purchase #3	$158.61	10.703%	$175.586	$175.59	$175.60	$175.60
Purchase #4	$125.36	9.141%	$136.8192	$136.82	$136.80	$136.80
Purchase #5	$205.52	8.489%	$222.9666	$222.97	$222.95	$223.00
Purchase #6	$140.28	8.477%	$152.1715	$152.17	$152.15	$152.20
Purchase #7	$134.30	7.601%	$144.5081	$144.51	$144.50	$144.50
7 purchase totals =	$929.45		$1,017.6853	$1,017.70	$1,017.65	$1,017.70