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	$149.88	8.732%	$162.9675	$162.97	$162.95	$163.00
Purchase #2	$69.41	11.322%	$77.2686	$77.27	$77.25	$77.30
Purchase #3	$10.27	3.398%	$10.619	$10.62	$10.60	$10.60
Purchase #4	$40.78	11.508%	$45.473	$45.47	$45.45	$45.50
Purchase #5	$163.84	5.281%	$172.4924	$172.49	$172.50	$172.50
Purchase #6	$113.51	10.222%	$125.113	$125.11	$125.10	$125.10
Purchase #7	$82.91	9.173%	$90.5153	$90.52	$90.50	$90.50
7 purchase totals =	$630.60		$684.4488	$684.45	$684.35	$684.50