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	$191.59	6.545%	$204.1296	$204.13	$204.15	$204.10
Purchase #2	$85.31	11.761%	$95.3433	$95.34	$95.35	$95.30
Purchase #3	$28.38	9.845%	$31.174	$31.17	$31.15	$31.20
Purchase #4	$92.31	11.472%	$102.8998	$102.90	$102.90	$102.90
Purchase #5	$127.83	10.123%	$140.7702	$140.77	$140.75	$140.80
Purchase #6	$69.38	12.793%	$78.2558	$78.26	$78.25	$78.30
Purchase #7	$60.62	10.321%	$66.8766	$66.88	$66.90	$66.90
7 purchase totals =	$655.42		$719.4493	$719.45	$719.45	$719.50