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	$183.30	7.392%	$196.8495	$196.85	$196.85	$196.80
Purchase #2	$17.85	13.780%	$20.3097	$20.31	$20.30	$20.30
Purchase #3	$121.91	4.823%	$127.7897	$127.79	$127.80	$127.80
Purchase #4	$142.59	11.164%	$158.5087	$158.51	$158.50	$158.50
Purchase #5	$223.95	8.867%	$243.8076	$243.81	$243.80	$243.80
Purchase #6	$93.25	4.781%	$97.7083	$97.71	$97.70	$97.70
Purchase #7	$116.49	11.157%	$129.4868	$129.49	$129.50	$129.50
7 purchase totals =	$899.34		$974.4603	$974.47	$974.45	$974.40