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	$228.39	12.132%	$256.0983	$256.10	$256.10	$256.10
Purchase #2	$68.62	8.505%	$74.4561	$74.46	$74.45	$74.50
Purchase #3	$46.64	13.665%	$53.0134	$53.01	$53.00	$53.00
Purchase #4	$171.54	10.776%	$190.0252	$190.03	$190.05	$190.00
Purchase #5	$76.60	8.310%	$82.9655	$82.97	$82.95	$83.00
Purchase #6	$47.94	4.489%	$50.092	$50.09	$50.10	$50.10
Purchase #7	$55.44	11.427%	$61.7751	$61.78	$61.80	$61.80
7 purchase totals =	$695.17		$768.4256	$768.44	$768.45	$768.50