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	$60.54	7.480%	$65.0684	$65.07	$65.05	$65.10
Purchase #2	$56.76	5.560%	$59.9159	$59.92	$59.90	$59.90
Purchase #3	$114.42	4.436%	$119.4957	$119.50	$119.50	$119.50
Purchase #4	$11.32	9.626%	$12.4097	$12.41	$12.40	$12.40
Purchase #5	$129.51	8.812%	$140.9224	$140.92	$140.90	$140.90
Purchase #6	$22.81	6.664%	$24.3301	$24.33	$24.35	$24.30
Purchase #7	$40.42	7.328%	$43.382	$43.38	$43.40	$43.40
7 purchase totals =	$435.78		$465.5242	$465.53	$465.50	$465.50