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	$216.34	10.162%	$238.3245	$238.32	$238.30	$238.30
Purchase #2	$30.75	8.430%	$33.3422	$33.34	$33.35	$33.30
Purchase #3	$37.43	10.436%	$41.3362	$41.34	$41.35	$41.30
Purchase #4	$64.46	5.394%	$67.937	$67.94	$67.95	$67.90
Purchase #5	$71.69	11.688%	$80.0691	$80.07	$80.05	$80.10
Purchase #6	$107.54	5.792%	$113.7687	$113.77	$113.75	$113.80
Purchase #7	$137.73	13.443%	$156.245	$156.25	$156.25	$156.20
7 purchase totals =	$665.94		$731.0227	$731.03	$731.00	$730.90