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	$125.34	5.588%	$132.344	$132.34	$132.35	$132.30
Purchase #2	$54.99	4.160%	$57.2776	$57.28	$57.30	$57.30
Purchase #3	$94.83	11.366%	$105.6084	$105.61	$105.60	$105.60
Purchase #4	$23.85	3.199%	$24.613	$24.61	$24.60	$24.60
Purchase #5	$250.53	11.859%	$280.2404	$280.24	$280.25	$280.20
Purchase #6	$148.52	11.167%	$165.1052	$165.11	$165.10	$165.10
Purchase #7	$164.82	7.221%	$176.7217	$176.72	$176.70	$176.70
7 purchase totals =	$862.88		$941.9103	$941.91	$941.90	$941.80