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	$96.27	8.573%	$104.5232	$104.52	$104.50	$104.50
Purchase #2	$139.25	7.806%	$150.1199	$150.12	$150.10	$150.10
Purchase #3	$161.31	6.695%	$172.1097	$172.11	$172.10	$172.10
Purchase #4	$229.43	7.140%	$245.8113	$245.81	$245.80	$245.80
Purchase #5	$230.39	7.757%	$248.2614	$248.26	$248.25	$248.30
Purchase #6	$78.85	9.180%	$86.0884	$86.09	$86.10	$86.10
Purchase #7	$242.77	11.459%	$270.589	$270.59	$270.60	$270.60
7 purchase totals =	$1,178.27		$1,277.5029	$1,277.50	$1,277.45	$1,277.50