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	$208.27	8.412%	$225.7897	$225.79	$225.80	$225.80
Purchase #2	$73.76	13.758%	$83.9079	$83.91	$83.90	$83.90
Purchase #3	$37.90	13.638%	$43.0688	$43.07	$43.05	$43.10
Purchase #4	$157.90	11.579%	$176.1832	$176.18	$176.20	$176.20
Purchase #5	$163.88	11.538%	$182.7885	$182.79	$182.80	$182.80
Purchase #6	$160.91	4.335%	$167.8854	$167.89	$167.90	$167.90
Purchase #7	$188.77	6.202%	$200.4775	$200.48	$200.50	$200.50
7 purchase totals =	$991.39		$1,080.1010	$1,080.11	$1,080.15	$1,080.20