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	$100.82	8.176%	$109.063	$109.06	$109.05	$109.10
Purchase #2	$171.52	5.221%	$180.4751	$180.48	$180.50	$180.50
Purchase #3	$92.34	13.788%	$105.0718	$105.07	$105.05	$105.10
Purchase #4	$34.27	8.527%	$37.1922	$37.19	$37.20	$37.20
Purchase #5	$83.81	12.341%	$94.153	$94.15	$94.15	$94.20
Purchase #6	$240.46	6.712%	$256.5997	$256.60	$256.60	$256.60
Purchase #7	$155.91	11.198%	$173.3688	$173.37	$173.35	$173.40
7 purchase totals =	$879.13		$955.9236	$955.92	$955.90	$956.10