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	$152.72	11.284%	$169.9529	$169.95	$169.95	$170.00
Purchase #2	$88.26	7.191%	$94.6068	$94.61	$94.60	$94.60
Purchase #3	$143.57	6.352%	$152.6896	$152.69	$152.70	$152.70
Purchase #4	$75.82	12.704%	$85.4522	$85.45	$85.45	$85.50
Purchase #5	$222.91	8.554%	$241.9777	$241.98	$242.00	$242.00
Purchase #6	$65.54	7.249%	$70.291	$70.29	$70.30	$70.30
Purchase #7	$238.29	7.149%	$255.3254	$255.33	$255.35	$255.30
7 purchase totals =	$987.11		$1,070.2956	$1,070.30	$1,070.35	$1,070.40