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	$112.92	5.482%	$119.1103	$119.11	$119.10	$119.10
Purchase #2	$61.35	5.169%	$64.5212	$64.52	$64.50	$64.50
Purchase #3	$61.79	8.609%	$67.1095	$67.11	$67.10	$67.10
Purchase #4	$145.35	10.690%	$160.8879	$160.89	$160.90	$160.90
Purchase #5	$119.95	6.379%	$127.6016	$127.60	$127.60	$127.60
Purchase #6	$139.79	7.637%	$150.4658	$150.47	$150.45	$150.50
Purchase #7	$149.99	8.377%	$162.5547	$162.55	$162.55	$162.60
7 purchase totals =	$791.14		$852.2510	$852.25	$852.20	$852.30