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	$79.28	3.521%	$82.0714	$82.07	$82.05	$82.10
Purchase #2	$71.73	5.579%	$75.7318	$75.73	$75.75	$75.70
Purchase #3	$155.54	3.814%	$161.4723	$161.47	$161.45	$161.50
Purchase #4	$221.30	7.826%	$238.6189	$238.62	$238.60	$238.60
Purchase #5	$24.47	4.449%	$25.5587	$25.56	$25.55	$25.60
Purchase #6	$149.87	9.754%	$164.4883	$164.49	$164.50	$164.50
Purchase #7	$54.96	8.335%	$59.5409	$59.54	$59.55	$59.50
7 purchase totals =	$757.15		$807.4823	$807.48	$807.45	$807.50