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	$241.41	8.345%	$261.5557	$261.56	$261.55	$261.60
Purchase #2	$148.25	11.428%	$165.192	$165.19	$165.20	$165.20
Purchase #3	$210.83	7.150%	$225.9043	$225.90	$225.90	$225.90
Purchase #4	$176.35	11.431%	$196.5086	$196.51	$196.50	$196.50
Purchase #5	$132.74	3.430%	$137.293	$137.29	$137.30	$137.30
Purchase #6	$140.69	7.182%	$150.7944	$150.79	$150.80	$150.80
Purchase #7	$227.43	13.120%	$257.2688	$257.27	$257.25	$257.30
7 purchase totals =	$1,277.70		$1,394.5168	$1,394.51	$1,394.50	$1,394.60