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	$111.94	6.364%	$119.0639	$119.06	$119.05	$119.10
Purchase #2	$111.86	13.152%	$126.5718	$126.57	$126.55	$126.60
Purchase #3	$170.84	12.429%	$192.0737	$192.07	$192.05	$192.10
Purchase #4	$35.61	5.323%	$37.5055	$37.51	$37.50	$37.50
Purchase #5	$173.96	11.660%	$194.2437	$194.24	$194.25	$194.20
Purchase #6	$180.37	11.300%	$200.7518	$200.75	$200.75	$200.80
Purchase #7	$205.49	12.672%	$231.5297	$231.53	$231.55	$231.50
7 purchase totals =	$990.07		$1,101.7401	$1,101.73	$1,101.70	$1,101.80