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	$137.44	11.713%	$153.5383	$153.54	$153.55	$153.50
Purchase #2	$209.69	7.604%	$225.6348	$225.63	$225.65	$225.60
Purchase #3	$216.32	12.624%	$243.6282	$243.63	$243.65	$243.60
Purchase #4	$156.58	5.715%	$165.5285	$165.53	$165.55	$165.50
Purchase #5	$6.50	10.167%	$7.1609	$7.16	$7.15	$7.20
Purchase #6	$170.54	10.561%	$188.5507	$188.55	$188.55	$188.60
Purchase #7	$96.91	8.848%	$105.4846	$105.48	$105.50	$105.50
7 purchase totals =	$993.98		$1,089.5260	$1,089.52	$1,089.60	$1,089.50