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	$151.33	11.451%	$168.6588	$168.66	$168.65	$168.70
Purchase #2	$41.66	10.469%	$46.0214	$46.02	$46.00	$46.00
Purchase #3	$179.61	10.756%	$198.9289	$198.93	$198.95	$198.90
Purchase #4	$13.80	7.545%	$14.8412	$14.84	$14.85	$14.80
Purchase #5	$12.42	5.182%	$13.0636	$13.06	$13.05	$13.10
Purchase #6	$54.35	10.203%	$59.8953	$59.90	$59.90	$59.90
Purchase #7	$13.89	11.529%	$15.4914	$15.49	$15.50	$15.50
7 purchase totals =	$467.06		$516.9006	$516.90	$516.90	$516.90