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	$136.63	8.861%	$148.7368	$148.74	$148.75	$148.70
Purchase #2	$59.54	10.130%	$65.5714	$65.57	$65.55	$65.60
Purchase #3	$75.30	8.253%	$81.5145	$81.51	$81.50	$81.50
Purchase #4	$111.76	6.731%	$119.2826	$119.28	$119.30	$119.30
Purchase #5	$60.67	11.178%	$67.4517	$67.45	$67.45	$67.50
Purchase #6	$151.31	12.693%	$170.5158	$170.52	$170.50	$170.50
Purchase #7	$106.43	4.862%	$111.6046	$111.60	$111.60	$111.60
7 purchase totals =	$701.64		$764.6774	$764.67	$764.65	$764.70