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	$110.41	3.595%	$114.3792	$114.38	$114.40	$114.40
Purchase #2	$222.37	4.533%	$232.45	$232.45	$232.45	$232.50
Purchase #3	$85.76	11.675%	$95.7725	$95.77	$95.75	$95.80
Purchase #4	$231.47	9.494%	$253.4458	$253.45	$253.45	$253.40
Purchase #5	$75.50	13.355%	$85.583	$85.58	$85.60	$85.60
Purchase #6	$50.45	5.511%	$53.2303	$53.23	$53.25	$53.20
Purchase #7	$61.91	8.753%	$67.329	$67.33	$67.35	$67.30
7 purchase totals =	$837.87		$902.1898	$902.19	$902.25	$902.20