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	$72.50	3.350%	$74.9288	$74.93	$74.95	$74.90
Purchase #2	$246.61	10.648%	$272.869	$272.87	$272.85	$272.90
Purchase #3	$68.49	5.394%	$72.1844	$72.18	$72.20	$72.20
Purchase #4	$51.29	6.214%	$54.4772	$54.48	$54.50	$54.50
Purchase #5	$158.92	6.684%	$169.5422	$169.54	$169.55	$169.50
Purchase #6	$110.37	11.631%	$123.2071	$123.21	$123.20	$123.20
Purchase #7	$129.69	5.105%	$136.3107	$136.31	$136.30	$136.30
7 purchase totals =	$837.87		$903.5194	$903.52	$903.55	$903.50