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	$201.45	10.136%	$221.869	$221.87	$221.85	$221.90
Purchase #2	$12.53	13.434%	$14.2133	$14.21	$14.20	$14.20
Purchase #3	$139.70	12.218%	$156.7685	$156.77	$156.75	$156.80
Purchase #4	$80.77	11.487%	$90.048	$90.05	$90.05	$90.00
Purchase #5	$33.39	11.345%	$37.1781	$37.18	$37.20	$37.20
Purchase #6	$162.36	6.484%	$172.8874	$172.89	$172.90	$172.90
Purchase #7	$5.61	5.366%	$5.911	$5.91	$5.90	$5.90
7 purchase totals =	$635.81		$698.8753	$698.88	$698.85	$698.90