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	$137.47	10.373%	$151.7298	$151.73	$151.75	$151.70
Purchase #2	$45.52	9.799%	$49.9805	$49.98	$50.00	$50.00
Purchase #3	$192.47	11.783%	$215.1487	$215.15	$215.15	$215.10
Purchase #4	$34.45	10.117%	$37.9353	$37.94	$37.95	$37.90
Purchase #5	$35.82	4.651%	$37.486	$37.49	$37.50	$37.50
Purchase #6	$11.62	7.537%	$12.4958	$12.50	$12.50	$12.50
Purchase #7	$225.56	6.416%	$240.0319	$240.03	$240.05	$240.00
7 purchase totals =	$682.91		$744.8080	$744.82	$744.90	$744.70