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	$59.70	4.231%	$62.2259	$62.23	$62.25	$62.20
Purchase #2	$140.53	8.401%	$152.3359	$152.34	$152.35	$152.30
Purchase #3	$61.42	10.444%	$67.8347	$67.83	$67.85	$67.80
Purchase #4	$58.72	9.590%	$64.3512	$64.35	$64.35	$64.40
Purchase #5	$39.59	7.188%	$42.4357	$42.44	$42.45	$42.40
Purchase #6	$100.44	11.205%	$111.6943	$111.69	$111.70	$111.70
Purchase #7	$100.87	10.498%	$111.4593	$111.46	$111.45	$111.50
7 purchase totals =	$561.27		$612.3370	$612.34	$612.40	$612.30