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	$41.94	11.106%	$46.5979	$46.60	$46.60	$46.60
Purchase #2	$111.92	13.723%	$127.2788	$127.28	$127.30	$127.30
Purchase #3	$163.85	12.513%	$184.3526	$184.35	$184.35	$184.40
Purchase #4	$237.46	7.620%	$255.5545	$255.55	$255.55	$255.60
Purchase #5	$65.87	11.862%	$73.6835	$73.68	$73.70	$73.70
Purchase #6	$74.84	4.801%	$78.4331	$78.43	$78.45	$78.40
Purchase #7	$54.34	13.430%	$61.6379	$61.64	$61.65	$61.60
7 purchase totals =	$750.22		$827.5383	$827.53	$827.60	$827.60