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	$164.53	13.321%	$186.447	$186.45	$186.45	$186.40
Purchase #2	$67.90	5.312%	$71.5068	$71.51	$71.50	$71.50
Purchase #3	$126.56	13.741%	$143.9506	$143.95	$143.95	$144.00
Purchase #4	$11.85	5.758%	$12.5323	$12.53	$12.55	$12.50
Purchase #5	$154.78	6.592%	$164.9831	$164.98	$165.00	$165.00
Purchase #6	$242.51	13.455%	$275.1397	$275.14	$275.15	$275.10
Purchase #7	$76.61	12.158%	$85.9242	$85.92	$85.90	$85.90
7 purchase totals =	$844.74		$940.4837	$940.48	$940.50	$940.40