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	$55.29	8.468%	$59.972	$59.97	$59.95	$60.00
Purchase #2	$168.49	4.776%	$176.5371	$176.54	$176.55	$176.50
Purchase #3	$148.60	13.597%	$168.8051	$168.81	$168.80	$168.80
Purchase #4	$38.89	5.658%	$41.0904	$41.09	$41.10	$41.10
Purchase #5	$9.57	10.740%	$10.5978	$10.60	$10.60	$10.60
Purchase #6	$165.64	8.363%	$179.4925	$179.49	$179.50	$179.50
Purchase #7	$33.56	12.198%	$37.6536	$37.65	$37.65	$37.70
7 purchase totals =	$620.04		$674.1485	$674.15	$674.15	$674.20