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	$94.90	7.769%	$102.2728	$102.27	$102.25	$102.30
Purchase #2	$29.67	13.355%	$33.6324	$33.63	$33.65	$33.60
Purchase #3	$149.45	11.410%	$166.5022	$166.50	$166.50	$166.50
Purchase #4	$120.31	3.367%	$124.3608	$124.36	$124.35	$124.40
Purchase #5	$180.85	3.344%	$186.8976	$186.90	$186.90	$186.90
Purchase #6	$173.43	13.324%	$196.5378	$196.54	$196.55	$196.50
Purchase #7	$128.45	13.259%	$145.4812	$145.48	$145.50	$145.50
7 purchase totals =	$877.06		$955.6848	$955.68	$955.70	$955.70