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	$155.73	12.777%	$175.6276	$175.63	$175.65	$175.60
Purchase #2	$6.90	10.332%	$7.6129	$7.61	$7.60	$7.60
Purchase #3	$210.38	13.446%	$238.6677	$238.67	$238.65	$238.70
Purchase #4	$30.47	11.230%	$33.8918	$33.89	$33.90	$33.90
Purchase #5	$140.42	11.735%	$156.8983	$156.90	$156.90	$156.90
Purchase #6	$133.64	8.468%	$144.9566	$144.96	$144.95	$145.00
Purchase #7	$37.97	10.163%	$41.8289	$41.83	$41.85	$41.80
7 purchase totals =	$715.51		$799.4838	$799.49	$799.50	$799.50