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	$35.61	4.512%	$37.2167	$37.22	$37.20	$37.20
Purchase #2	$247.41	12.124%	$277.406	$277.41	$277.40	$277.40
Purchase #3	$73.89	6.163%	$78.4438	$78.44	$78.45	$78.40
Purchase #4	$215.71	4.743%	$225.9411	$225.94	$225.95	$225.90
Purchase #5	$215.51	13.118%	$243.7806	$243.78	$243.80	$243.80
Purchase #6	$68.84	8.197%	$74.4828	$74.48	$74.50	$74.50
Purchase #7	$110.96	3.506%	$114.8503	$114.85	$114.85	$114.90
7 purchase totals =	$967.93		$1,052.1213	$1,052.12	$1,052.15	$1,052.10