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	$85.51	3.779%	$88.7414	$88.74	$88.75	$88.70
Purchase #2	$103.85	7.144%	$111.269	$111.27	$111.25	$111.30
Purchase #3	$47.34	13.680%	$53.8161	$53.82	$53.80	$53.80
Purchase #4	$219.39	7.682%	$236.2435	$236.24	$236.25	$236.20
Purchase #5	$41.67	13.483%	$47.2884	$47.29	$47.30	$47.30
Purchase #6	$67.27	12.394%	$75.6074	$75.61	$75.60	$75.60
Purchase #7	$126.35	10.397%	$139.4866	$139.49	$139.50	$139.50
7 purchase totals =	$691.38		$752.4524	$752.46	$752.45	$752.40