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	$224.51	8.655%	$243.9413	$243.94	$243.95	$243.90
Purchase #2	$178.32	7.693%	$192.0382	$192.04	$192.05	$192.00
Purchase #3	$111.58	6.855%	$119.2288	$119.23	$119.25	$119.20
Purchase #4	$196.76	5.746%	$208.0658	$208.07	$208.05	$208.10
Purchase #5	$73.53	13.591%	$83.5235	$83.52	$83.50	$83.50
Purchase #6	$21.58	4.292%	$22.5062	$22.51	$22.50	$22.50
Purchase #7	$208.44	13.159%	$235.8686	$235.87	$235.85	$235.90
7 purchase totals =	$1,014.72		$1,105.1724	$1,105.18	$1,105.15	$1,105.10