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	$85.89	7.613%	$92.4288	$92.43	$92.45	$92.40
Purchase #2	$10.73	11.545%	$11.9688	$11.97	$11.95	$12.00
Purchase #3	$66.64	8.848%	$72.5363	$72.54	$72.55	$72.50
Purchase #4	$10.29	12.852%	$11.6125	$11.61	$11.60	$11.60
Purchase #5	$83.70	5.769%	$88.5287	$88.53	$88.55	$88.50
Purchase #6	$44.88	7.551%	$48.2689	$48.27	$48.25	$48.30
Purchase #7	$146.98	8.188%	$159.0147	$159.01	$159.00	$159.00
7 purchase totals =	$449.11		$484.3587	$484.36	$484.35	$484.30