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	$154.73	6.725%	$165.1356	$165.14	$165.15	$165.10
Purchase #2	$113.53	11.217%	$126.2647	$126.26	$126.25	$126.30
Purchase #3	$148.27	7.132%	$158.8446	$158.84	$158.85	$158.80
Purchase #4	$240.65	4.473%	$251.4143	$251.41	$251.40	$251.40
Purchase #5	$143.34	5.486%	$151.2036	$151.20	$151.20	$151.20
Purchase #6	$178.38	12.205%	$200.1513	$200.15	$200.15	$200.20
Purchase #7	$185.60	8.236%	$200.886	$200.89	$200.90	$200.90
7 purchase totals =	$1,164.50		$1,253.9001	$1,253.89	$1,253.90	$1,253.90