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	$109.40	9.756%	$120.0731	$120.07	$120.05	$120.10
Purchase #2	$177.33	10.808%	$196.4958	$196.50	$196.50	$196.50
Purchase #3	$74.51	5.474%	$78.5887	$78.59	$78.60	$78.60
Purchase #4	$45.94	10.192%	$50.6222	$50.62	$50.60	$50.60
Purchase #5	$37.54	10.810%	$41.5981	$41.60	$41.60	$41.60
Purchase #6	$10.38	5.825%	$10.9846	$10.98	$11.00	$11.00
Purchase #7	$14.64	10.122%	$16.1219	$16.12	$16.10	$16.10
7 purchase totals =	$469.74		$514.4844	$514.48	$514.45	$514.50