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	$151.73	6.430%	$161.4862	$161.49	$161.50	$161.50
Purchase #2	$104.31	11.676%	$116.4892	$116.49	$116.50	$116.50
Purchase #3	$66.43	8.539%	$72.1025	$72.10	$72.10	$72.10
Purchase #4	$241.58	13.106%	$273.2415	$273.24	$273.25	$273.20
Purchase #5	$110.38	5.449%	$116.3946	$116.39	$116.40	$116.40
Purchase #6	$165.52	6.425%	$176.1547	$176.15	$176.15	$176.20
Purchase #7	$135.53	11.491%	$151.1038	$151.10	$151.10	$151.10
7 purchase totals =	$975.48		$1,066.9725	$1,066.96	$1,067.00	$1,067.00