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	$160.60	3.268%	$165.8484	$165.85	$165.85	$165.80
Purchase #2	$122.96	10.206%	$135.5093	$135.51	$135.50	$135.50
Purchase #3	$24.58	4.102%	$25.5883	$25.59	$25.60	$25.60
Purchase #4	$100.53	11.273%	$111.8627	$111.86	$111.85	$111.90
Purchase #5	$26.51	7.149%	$28.4052	$28.41	$28.40	$28.40
Purchase #6	$146.54	6.456%	$156.0006	$156.00	$156.00	$156.00
Purchase #7	$112.25	11.839%	$125.5393	$125.54	$125.55	$125.50
7 purchase totals =	$693.97		$748.7538	$748.76	$748.75	$748.70