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	$232.47	13.800%	$264.5509	$264.55	$264.55	$264.60
Purchase #2	$233.50	4.141%	$243.1692	$243.17	$243.15	$243.20
Purchase #3	$8.30	6.155%	$8.8109	$8.81	$8.80	$8.80
Purchase #4	$80.40	11.825%	$89.9073	$89.91	$89.90	$89.90
Purchase #5	$24.96	7.560%	$26.847	$26.85	$26.85	$26.80
Purchase #6	$226.85	3.520%	$234.8351	$234.84	$234.85	$234.80
Purchase #7	$161.82	6.592%	$172.4872	$172.49	$172.50	$172.50
7 purchase totals =	$968.30		$1,040.6076	$1,040.62	$1,040.60	$1,040.60