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	$172.57	13.130%	$195.2284	$195.23	$195.25	$195.20
Purchase #2	$199.48	4.731%	$208.9174	$208.92	$208.90	$208.90
Purchase #3	$40.76	9.538%	$44.6477	$44.65	$44.65	$44.60
Purchase #4	$68.60	5.769%	$72.5575	$72.56	$72.55	$72.60
Purchase #5	$99.31	6.185%	$105.4523	$105.45	$105.45	$105.50
Purchase #6	$32.47	7.222%	$34.815	$34.82	$34.80	$34.80
Purchase #7	$41.38	3.158%	$42.6868	$42.69	$42.70	$42.70
7 purchase totals =	$654.57		$704.3051	$704.32	$704.30	$704.30