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	$241.54	9.245%	$263.8704	$263.87	$263.85	$263.90
Purchase #2	$117.59	9.388%	$128.6293	$128.63	$128.65	$128.60
Purchase #3	$150.88	3.304%	$155.8651	$155.87	$155.85	$155.90
Purchase #4	$242.47	12.242%	$272.1532	$272.15	$272.15	$272.20
Purchase #5	$221.94	13.332%	$251.529	$251.53	$251.55	$251.50
Purchase #6	$37.79	4.532%	$39.5026	$39.50	$39.50	$39.50
Purchase #7	$138.95	8.260%	$150.4273	$150.43	$150.45	$150.40
7 purchase totals =	$1,151.16		$1,261.9769	$1,261.98	$1,262.00	$1,262.00