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	$29.85	10.133%	$32.8747	$32.87	$32.85	$32.90
Purchase #2	$67.90	7.402%	$72.926	$72.93	$72.95	$72.90
Purchase #3	$83.33	6.746%	$88.9514	$88.95	$88.95	$89.00
Purchase #4	$77.56	7.862%	$83.6578	$83.66	$83.65	$83.70
Purchase #5	$62.30	13.176%	$70.5086	$70.51	$70.50	$70.50
Purchase #6	$250.95	11.525%	$279.872	$279.87	$279.85	$279.90
Purchase #7	$50.94	7.780%	$54.9031	$54.90	$54.90	$54.90
7 purchase totals =	$622.83		$683.6936	$683.69	$683.65	$683.80