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	$217.33	5.477%	$229.2332	$229.23	$229.25	$229.20
Purchase #2	$103.29	6.675%	$110.1846	$110.18	$110.20	$110.20
Purchase #3	$41.34	9.805%	$45.3934	$45.39	$45.40	$45.40
Purchase #4	$125.96	13.840%	$143.3929	$143.39	$143.40	$143.40
Purchase #5	$38.68	4.723%	$40.5069	$40.51	$40.50	$40.50
Purchase #6	$89.86	9.755%	$98.6258	$98.63	$98.65	$98.60
Purchase #7	$45.67	9.520%	$50.0178	$50.02	$50.00	$50.00
7 purchase totals =	$662.13		$717.3546	$717.35	$717.40	$717.30