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	$137.44	10.605%	$152.0155	$152.02	$152.00	$152.00
Purchase #2	$225.56	5.670%	$238.3493	$238.35	$238.35	$238.30
Purchase #3	$62.42	6.733%	$66.6227	$66.62	$66.60	$66.60
Purchase #4	$118.78	10.203%	$130.8991	$130.90	$130.90	$130.90
Purchase #5	$59.79	13.342%	$67.7672	$67.77	$67.75	$67.80
Purchase #6	$173.30	3.869%	$180.005	$180.01	$180.00	$180.00
Purchase #7	$94.67	4.803%	$99.217	$99.22	$99.20	$99.20
7 purchase totals =	$871.96		$934.8758	$934.89	$934.80	$934.80