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	$111.85	11.660%	$124.8917	$124.89	$124.90	$124.90
Purchase #2	$153.78	8.117%	$166.2623	$166.26	$166.25	$166.30
Purchase #3	$115.44	9.434%	$126.3306	$126.33	$126.35	$126.30
Purchase #4	$86.46	3.459%	$89.4507	$89.45	$89.45	$89.50
Purchase #5	$186.47	8.576%	$202.4617	$202.46	$202.45	$202.50
Purchase #6	$90.52	8.790%	$98.4767	$98.48	$98.50	$98.50
Purchase #7	$12.89	10.313%	$14.2193	$14.22	$14.20	$14.20
7 purchase totals =	$757.41		$822.0930	$822.09	$822.10	$822.20