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	$201.71	7.385%	$216.6063	$216.61	$216.60	$216.60
Purchase #2	$78.31	3.707%	$81.213	$81.21	$81.20	$81.20
Purchase #3	$237.80	6.625%	$253.5543	$253.55	$253.55	$253.60
Purchase #4	$89.82	5.604%	$94.8535	$94.85	$94.85	$94.90
Purchase #5	$89.94	6.150%	$95.4713	$95.47	$95.45	$95.50
Purchase #6	$207.74	7.143%	$222.5789	$222.58	$222.60	$222.60
Purchase #7	$222.70	7.149%	$238.6208	$238.62	$238.60	$238.60
7 purchase totals =	$1,128.02		$1,202.8981	$1,202.89	$1,202.85	$1,203.00