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	$74.36	10.546%	$82.202	$82.20	$82.20	$82.20
Purchase #2	$209.62	4.312%	$218.6588	$218.66	$218.65	$218.70
Purchase #3	$40.27	6.871%	$43.037	$43.04	$43.05	$43.00
Purchase #4	$61.25	9.614%	$67.1386	$67.14	$67.15	$67.10
Purchase #5	$185.29	11.120%	$205.8942	$205.89	$205.90	$205.90
Purchase #6	$37.38	6.782%	$39.9151	$39.92	$39.90	$39.90
Purchase #7	$155.59	3.386%	$160.8583	$160.86	$160.85	$160.90
7 purchase totals =	$763.76		$817.7040	$817.71	$817.70	$817.70