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	$229.87	3.406%	$237.6994	$237.70	$237.70	$237.70
Purchase #2	$81.73	9.622%	$89.5941	$89.59	$89.60	$89.60
Purchase #3	$112.54	3.171%	$116.1086	$116.11	$116.10	$116.10
Purchase #4	$203.77	8.808%	$221.7181	$221.72	$221.70	$221.70
Purchase #5	$30.26	10.701%	$33.4981	$33.50	$33.50	$33.50
Purchase #6	$141.95	7.176%	$152.1363	$152.14	$152.15	$152.10
Purchase #7	$141.35	13.459%	$160.3743	$160.37	$160.35	$160.40
7 purchase totals =	$941.47		$1,011.1289	$1,011.13	$1,011.10	$1,011.10