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	$172.48	13.704%	$196.1167	$196.12	$196.10	$196.10
Purchase #2	$37.28	8.222%	$40.3452	$40.35	$40.35	$40.30
Purchase #3	$78.94	4.214%	$82.2665	$82.27	$82.25	$82.30
Purchase #4	$194.51	7.546%	$209.1877	$209.19	$209.20	$209.20
Purchase #5	$107.71	8.303%	$116.6532	$116.65	$116.65	$116.70
Purchase #6	$106.96	13.533%	$121.4349	$121.43	$121.45	$121.40
Purchase #7	$165.62	7.498%	$178.0382	$178.04	$178.05	$178.00
7 purchase totals =	$863.50		$944.0424	$944.05	$944.05	$944.00