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	$59.98	8.655%	$65.1713	$65.17	$65.15	$65.20
Purchase #2	$170.74	12.402%	$191.9152	$191.92	$191.90	$191.90
Purchase #3	$200.67	5.377%	$211.46	$211.46	$211.45	$211.50
Purchase #4	$41.81	9.767%	$45.8936	$45.89	$45.90	$45.90
Purchase #5	$47.95	11.114%	$53.2792	$53.28	$53.30	$53.30
Purchase #6	$113.53	11.483%	$126.5666	$126.57	$126.55	$126.60
Purchase #7	$49.98	10.382%	$55.1689	$55.17	$55.15	$55.20
7 purchase totals =	$684.66		$749.4548	$749.46	$749.40	$749.60