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	$221.61	12.690%	$249.7323	$249.73	$249.75	$249.70
Purchase #2	$57.73	6.246%	$61.3358	$61.34	$61.35	$61.30
Purchase #3	$156.69	8.301%	$169.6968	$169.70	$169.70	$169.70
Purchase #4	$148.90	12.497%	$167.508	$167.51	$167.50	$167.50
Purchase #5	$126.94	11.444%	$141.467	$141.47	$141.45	$141.50
Purchase #6	$172.52	6.754%	$184.172	$184.17	$184.15	$184.20
Purchase #7	$133.35	7.495%	$143.3446	$143.34	$143.35	$143.30
7 purchase totals =	$1,017.74		$1,117.2565	$1,117.26	$1,117.25	$1,117.20