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	$55.90	9.247%	$61.0691	$61.07	$61.05	$61.10
Purchase #2	$42.54	3.190%	$43.897	$43.90	$43.90	$43.90
Purchase #3	$33.35	7.318%	$35.7906	$35.79	$35.80	$35.80
Purchase #4	$108.54	6.772%	$115.8903	$115.89	$115.90	$115.90
Purchase #5	$6.52	6.261%	$6.9282	$6.93	$6.95	$6.90
Purchase #6	$129.85	3.733%	$134.6973	$134.70	$134.70	$134.70
Purchase #7	$85.96	4.135%	$89.5144	$89.51	$89.50	$89.50
7 purchase totals =	$462.66		$487.7869	$487.79	$487.80	$487.80