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	$135.72	4.225%	$141.4542	$141.45	$141.45	$141.50
Purchase #2	$217.27	7.187%	$232.8852	$232.89	$232.90	$232.90
Purchase #3	$240.50	13.199%	$272.2436	$272.24	$272.25	$272.20
Purchase #4	$39.32	4.733%	$41.181	$41.18	$41.20	$41.20
Purchase #5	$62.87	13.294%	$71.2279	$71.23	$71.25	$71.20
Purchase #6	$119.35	3.131%	$123.0868	$123.09	$123.10	$123.10
Purchase #7	$207.66	13.130%	$234.9258	$234.93	$234.95	$234.90
7 purchase totals =	$1,022.69		$1,117.0045	$1,117.01	$1,117.10	$1,117.00