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	$137.72	8.140%	$148.9304	$148.93	$148.95	$148.90
Purchase #2	$104.38	6.375%	$111.0342	$111.03	$111.05	$111.00
Purchase #3	$19.91	5.660%	$21.0369	$21.04	$21.05	$21.00
Purchase #4	$206.96	12.215%	$232.2402	$232.24	$232.25	$232.20
Purchase #5	$14.82	4.824%	$15.5349	$15.53	$15.55	$15.50
Purchase #6	$84.58	13.373%	$95.8909	$95.89	$95.90	$95.90
Purchase #7	$234.86	11.333%	$261.4767	$261.48	$261.50	$261.50
7 purchase totals =	$803.23		$886.1442	$886.14	$886.25	$886.00