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	$29.98	8.150%	$32.4234	$32.42	$32.40	$32.40
Purchase #2	$71.99	7.779%	$77.5901	$77.59	$77.60	$77.60
Purchase #3	$184.73	4.191%	$192.472	$192.47	$192.45	$192.50
Purchase #4	$31.32	11.358%	$34.8773	$34.88	$34.90	$34.90
Purchase #5	$32.67	12.361%	$36.7083	$36.71	$36.70	$36.70
Purchase #6	$76.63	11.709%	$85.6026	$85.60	$85.60	$85.60
Purchase #7	$21.72	4.363%	$22.6676	$22.67	$22.65	$22.70
7 purchase totals =	$449.04		$482.3413	$482.34	$482.30	$482.40