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	$104.51	7.566%	$112.4172	$112.42	$112.40	$112.40
Purchase #2	$145.34	3.240%	$150.049	$150.05	$150.05	$150.00
Purchase #3	$185.37	7.509%	$199.2894	$199.29	$199.30	$199.30
Purchase #4	$122.79	12.134%	$137.6893	$137.69	$137.70	$137.70
Purchase #5	$78.49	8.373%	$85.062	$85.06	$85.05	$85.10
Purchase #6	$13.83	5.578%	$14.6014	$14.60	$14.60	$14.60
Purchase #7	$113.55	11.406%	$126.5015	$126.50	$126.50	$126.50
7 purchase totals =	$763.88		$825.6098	$825.61	$825.60	$825.60