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	$142.55	12.346%	$160.1492	$160.15	$160.15	$160.10
Purchase #2	$29.87	8.643%	$32.4517	$32.45	$32.45	$32.50
Purchase #3	$221.51	6.459%	$235.8173	$235.82	$235.80	$235.80
Purchase #4	$74.88	4.789%	$78.466	$78.47	$78.45	$78.50
Purchase #5	$31.29	12.405%	$35.1715	$35.17	$35.15	$35.20
Purchase #6	$40.69	12.847%	$45.9174	$45.92	$45.90	$45.90
Purchase #7	$146.50	3.291%	$151.3213	$151.32	$151.30	$151.30
7 purchase totals =	$687.29		$739.2944	$739.30	$739.20	$739.30