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	$88.50	12.607%	$99.6572	$99.66	$99.65	$99.70
Purchase #2	$247.89	4.734%	$259.6251	$259.63	$259.65	$259.60
Purchase #3	$162.56	4.375%	$169.672	$169.67	$169.65	$169.70
Purchase #4	$158.63	10.700%	$175.6034	$175.60	$175.60	$175.60
Purchase #5	$244.85	4.823%	$256.6591	$256.66	$256.65	$256.70
Purchase #6	$49.57	11.806%	$55.4222	$55.42	$55.40	$55.40
Purchase #7	$135.39	6.260%	$143.8654	$143.87	$143.85	$143.90
7 purchase totals =	$1,087.39		$1,160.5044	$1,160.51	$1,160.45	$1,160.60