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	$237.43	8.389%	$257.348	$257.35	$257.35	$257.30
Purchase #2	$239.34	8.356%	$259.3393	$259.34	$259.35	$259.30
Purchase #3	$154.44	5.118%	$162.3442	$162.34	$162.35	$162.30
Purchase #4	$233.64	7.575%	$251.3382	$251.34	$251.35	$251.30
Purchase #5	$78.69	6.581%	$83.8686	$83.87	$83.85	$83.90
Purchase #6	$247.55	11.103%	$275.0355	$275.04	$275.05	$275.00
Purchase #7	$65.89	8.131%	$71.2475	$71.25	$71.25	$71.20
7 purchase totals =	$1,256.98		$1,360.5213	$1,360.53	$1,360.55	$1,360.30