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	$222.90	9.201%	$243.409	$243.41	$243.40	$243.40
Purchase #2	$236.81	13.785%	$269.4543	$269.45	$269.45	$269.50
Purchase #3	$59.66	11.110%	$66.2882	$66.29	$66.30	$66.30
Purchase #4	$116.98	6.759%	$124.8867	$124.89	$124.90	$124.90
Purchase #5	$144.91	4.516%	$151.4541	$151.45	$151.45	$151.50
Purchase #6	$49.88	9.254%	$54.4959	$54.50	$54.50	$54.50
Purchase #7	$151.67	13.682%	$172.4215	$172.42	$172.40	$172.40
7 purchase totals =	$982.81		$1,082.4097	$1,082.41	$1,082.40	$1,082.50