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	$64.60	7.166%	$69.2292	$69.23	$69.25	$69.20
Purchase #2	$48.69	8.351%	$52.7561	$52.76	$52.75	$52.80
Purchase #3	$128.25	11.248%	$142.6756	$142.68	$142.70	$142.70
Purchase #4	$199.62	8.464%	$216.5158	$216.52	$216.50	$216.50
Purchase #5	$33.64	10.477%	$37.1645	$37.16	$37.15	$37.20
Purchase #6	$186.58	5.512%	$196.8643	$196.86	$196.85	$196.90
Purchase #7	$146.52	6.816%	$156.5068	$156.51	$156.50	$156.50
7 purchase totals =	$807.90		$871.7123	$871.72	$871.70	$871.80