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	$129.56	3.188%	$133.6904	$133.69	$133.70	$133.70
Purchase #2	$65.25	11.413%	$72.697	$72.70	$72.70	$72.70
Purchase #3	$59.48	13.186%	$67.323	$67.32	$67.30	$67.30
Purchase #4	$126.29	13.645%	$143.5223	$143.52	$143.50	$143.50
Purchase #5	$38.59	12.528%	$43.4246	$43.42	$43.40	$43.40
Purchase #6	$192.52	7.667%	$207.2805	$207.28	$207.30	$207.30
Purchase #7	$196.25	6.610%	$209.2221	$209.22	$209.20	$209.20
7 purchase totals =	$807.94		$877.1599	$877.15	$877.10	$877.10