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	$143.86	8.384%	$155.9212	$155.92	$155.90	$155.90
Purchase #2	$52.43	4.572%	$54.8271	$54.83	$54.85	$54.80
Purchase #3	$8.38	5.175%	$8.8137	$8.81	$8.80	$8.80
Purchase #4	$105.73	3.156%	$109.0668	$109.07	$109.05	$109.10
Purchase #5	$163.68	4.545%	$171.1193	$171.12	$171.10	$171.10
Purchase #6	$94.48	11.293%	$105.1496	$105.15	$105.15	$105.10
Purchase #7	$234.57	4.406%	$244.9052	$244.91	$244.90	$244.90
7 purchase totals =	$803.13		$849.8029	$849.81	$849.75	$849.70