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	$52.67	13.107%	$59.5735	$59.57	$59.55	$59.60
Purchase #2	$194.87	4.188%	$203.0312	$203.03	$203.05	$203.00
Purchase #3	$76.52	9.175%	$83.5407	$83.54	$83.55	$83.50
Purchase #4	$158.60	6.401%	$168.752	$168.75	$168.75	$168.80
Purchase #5	$86.33	4.468%	$90.1872	$90.19	$90.20	$90.20
Purchase #6	$19.35	4.853%	$20.2891	$20.29	$20.30	$20.30
Purchase #7	$75.65	12.159%	$84.8483	$84.85	$84.85	$84.80
7 purchase totals =	$663.99		$710.2220	$710.22	$710.25	$710.20