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	$250.61	12.137%	$281.0265	$281.03	$281.05	$281.00
Purchase #2	$179.54	6.726%	$191.6159	$191.62	$191.60	$191.60
Purchase #3	$93.70	6.272%	$99.5769	$99.58	$99.60	$99.60
Purchase #4	$72.89	7.733%	$78.5266	$78.53	$78.55	$78.50
Purchase #5	$213.48	4.561%	$223.2168	$223.22	$223.20	$223.20
Purchase #6	$198.90	9.230%	$217.2585	$217.26	$217.25	$217.30
Purchase #7	$129.37	12.694%	$145.7922	$145.79	$145.80	$145.80
7 purchase totals =	$1,138.49		$1,237.0134	$1,237.03	$1,237.05	$1,237.00