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	$55.82	7.724%	$60.1315	$60.13	$60.15	$60.10
Purchase #2	$90.51	11.166%	$100.6163	$100.62	$100.60	$100.60
Purchase #3	$246.58	13.193%	$279.1113	$279.11	$279.10	$279.10
Purchase #4	$118.72	12.873%	$134.0028	$134.00	$134.00	$134.00
Purchase #5	$119.61	7.726%	$128.8511	$128.85	$128.85	$128.90
Purchase #6	$202.28	10.125%	$222.7609	$222.76	$222.75	$222.80
Purchase #7	$168.59	4.328%	$175.8866	$175.89	$175.90	$175.90
7 purchase totals =	$1,002.11		$1,101.3605	$1,101.36	$1,101.35	$1,101.40