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	$233.40	7.741%	$251.4675	$251.47	$251.45	$251.50
Purchase #2	$164.57	7.816%	$177.4328	$177.43	$177.45	$177.40
Purchase #3	$166.65	11.441%	$185.7164	$185.72	$185.70	$185.70
Purchase #4	$191.56	4.431%	$200.048	$200.05	$200.05	$200.00
Purchase #5	$149.69	6.440%	$159.33	$159.33	$159.35	$159.30
Purchase #6	$47.31	6.867%	$50.5588	$50.56	$50.55	$50.60
Purchase #7	$50.69	10.402%	$55.9628	$55.96	$55.95	$56.00
7 purchase totals =	$1,003.87		$1,080.5163	$1,080.52	$1,080.50	$1,080.50