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	$131.51	7.485%	$141.3535	$141.35	$141.35	$141.40
Purchase #2	$112.95	3.493%	$116.8953	$116.90	$116.90	$116.90
Purchase #3	$97.76	10.472%	$107.9974	$108.00	$108.00	$108.00
Purchase #4	$151.39	5.774%	$160.1313	$160.13	$160.15	$160.10
Purchase #5	$65.72	10.543%	$72.6489	$72.65	$72.65	$72.60
Purchase #6	$85.34	5.713%	$90.2155	$90.22	$90.20	$90.20
Purchase #7	$159.78	3.605%	$165.5401	$165.54	$165.55	$165.50
7 purchase totals =	$804.45		$854.7820	$854.79	$854.80	$854.70