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	$54.31	11.595%	$60.6072	$60.61	$60.60	$60.60
Purchase #2	$11.26	11.317%	$12.5343	$12.53	$12.55	$12.50
Purchase #3	$137.87	10.873%	$152.8606	$152.86	$152.85	$152.90
Purchase #4	$137.83	13.705%	$156.7196	$156.72	$156.70	$156.70
Purchase #5	$195.61	10.674%	$216.4894	$216.49	$216.50	$216.50
Purchase #6	$186.84	6.845%	$199.6292	$199.63	$199.65	$199.60
Purchase #7	$80.59	12.549%	$90.7032	$90.70	$90.70	$90.70
7 purchase totals =	$804.31		$889.5435	$889.54	$889.55	$889.50