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	$94.43	5.749%	$99.8588	$99.86	$99.85	$99.90
Purchase #2	$188.73	13.874%	$214.9144	$214.91	$214.90	$214.90
Purchase #3	$95.65	10.173%	$105.3805	$105.38	$105.40	$105.40
Purchase #4	$39.47	13.493%	$44.7957	$44.80	$44.80	$44.80
Purchase #5	$80.96	12.412%	$91.0088	$91.01	$91.00	$91.00
Purchase #6	$152.69	9.850%	$167.73	$167.73	$167.75	$167.70
Purchase #7	$168.84	5.239%	$177.6855	$177.69	$177.70	$177.70
7 purchase totals =	$820.77		$901.3737	$901.38	$901.40	$901.40