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	$82.74	7.366%	$88.8346	$88.83	$88.85	$88.80
Purchase #2	$21.38	5.512%	$22.5585	$22.56	$22.55	$22.60
Purchase #3	$98.92	4.783%	$103.6513	$103.65	$103.65	$103.70
Purchase #4	$10.30	10.664%	$11.3984	$11.40	$11.40	$11.40
Purchase #5	$245.89	6.605%	$262.131	$262.13	$262.15	$262.10
Purchase #6	$39.83	13.795%	$45.3245	$45.32	$45.30	$45.30
Purchase #7	$57.34	7.498%	$61.6394	$61.64	$61.65	$61.60
7 purchase totals =	$556.40		$595.5377	$595.53	$595.55	$595.50