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	$14.52	6.521%	$15.4668	$15.47	$15.45	$15.50
Purchase #2	$45.32	6.635%	$48.327	$48.33	$48.35	$48.30
Purchase #3	$183.62	8.711%	$199.6151	$199.62	$199.60	$199.60
Purchase #4	$213.55	7.196%	$228.9171	$228.92	$228.90	$228.90
Purchase #5	$113.96	4.845%	$119.4814	$119.48	$119.50	$119.50
Purchase #6	$94.66	5.500%	$99.8663	$99.87	$99.85	$99.90
Purchase #7	$85.29	10.812%	$94.5116	$94.51	$94.50	$94.50
7 purchase totals =	$750.92		$806.1853	$806.20	$806.15	$806.20