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	$196.34	13.168%	$222.1941	$222.19	$222.20	$222.20
Purchase #2	$237.90	7.397%	$255.4975	$255.50	$255.50	$255.50
Purchase #3	$223.85	12.389%	$251.5828	$251.58	$251.60	$251.60
Purchase #4	$126.37	3.109%	$130.2988	$130.30	$130.30	$130.30
Purchase #5	$242.76	11.426%	$270.4978	$270.50	$270.50	$270.50
Purchase #6	$155.61	13.638%	$176.8321	$176.83	$176.85	$176.80
Purchase #7	$157.27	8.820%	$171.1412	$171.14	$171.15	$171.10
7 purchase totals =	$1,340.10		$1,478.0443	$1,478.04	$1,478.10	$1,478.00