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	$59.84	4.453%	$62.5047	$62.50	$62.50	$62.50
Purchase #2	$89.83	3.573%	$93.0396	$93.04	$93.05	$93.00
Purchase #3	$108.91	8.697%	$118.3819	$118.38	$118.40	$118.40
Purchase #4	$126.98	3.645%	$131.6084	$131.61	$131.60	$131.60
Purchase #5	$39.54	7.628%	$42.5561	$42.56	$42.55	$42.60
Purchase #6	$220.71	9.827%	$242.3992	$242.40	$242.40	$242.40
Purchase #7	$120.35	5.208%	$126.6178	$126.62	$126.60	$126.60
7 purchase totals =	$766.16		$817.1077	$817.11	$817.10	$817.10