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	$116.89	9.451%	$127.9373	$127.94	$127.95	$127.90
Purchase #2	$180.70	13.772%	$205.586	$205.59	$205.60	$205.60
Purchase #3	$182.77	7.776%	$196.9822	$196.98	$197.00	$197.00
Purchase #4	$78.66	9.527%	$86.1539	$86.15	$86.15	$86.20
Purchase #5	$235.87	6.698%	$251.6686	$251.67	$251.65	$251.70
Purchase #6	$140.55	4.226%	$146.4896	$146.49	$146.50	$146.50
Purchase #7	$68.31	13.660%	$77.6411	$77.64	$77.65	$77.60
7 purchase totals =	$1,003.75		$1,092.4587	$1,092.46	$1,092.50	$1,092.50