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	$143.34	6.276%	$152.336	$152.34	$152.35	$152.30
Purchase #2	$19.37	10.167%	$21.3393	$21.34	$21.35	$21.30
Purchase #3	$222.55	5.198%	$234.1181	$234.12	$234.10	$234.10
Purchase #4	$68.77	4.570%	$71.9128	$71.91	$71.90	$71.90
Purchase #5	$239.89	4.175%	$249.9054	$249.91	$249.90	$249.90
Purchase #6	$14.34	10.584%	$15.8577	$15.86	$15.85	$15.90
Purchase #7	$120.68	7.584%	$129.8324	$129.83	$129.85	$129.80
7 purchase totals =	$828.94		$875.3017	$875.31	$875.30	$875.20