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	$230.90	7.425%	$248.0443	$248.04	$248.05	$248.00
Purchase #2	$39.77	9.868%	$43.6945	$43.69	$43.70	$43.70
Purchase #3	$170.54	3.624%	$176.7204	$176.72	$176.70	$176.70
Purchase #4	$87.50	6.167%	$92.8961	$92.90	$92.90	$92.90
Purchase #5	$119.45	6.697%	$127.4496	$127.45	$127.45	$127.40
Purchase #6	$194.51	11.811%	$217.4836	$217.48	$217.50	$217.50
Purchase #7	$223.63	9.797%	$245.539	$245.54	$245.55	$245.50
7 purchase totals =	$1,066.30		$1,151.8275	$1,151.82	$1,151.85	$1,151.70