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	$210.72	6.269%	$223.93	$223.93	$223.95	$223.90
Purchase #2	$118.96	3.247%	$122.8226	$122.82	$122.80	$122.80
Purchase #3	$226.53	8.508%	$245.8032	$245.80	$245.80	$245.80
Purchase #4	$218.31	11.770%	$244.0051	$244.01	$244.00	$244.00
Purchase #5	$78.80	13.727%	$89.6169	$89.62	$89.60	$89.60
Purchase #6	$117.82	4.439%	$123.05	$123.05	$123.05	$123.10
Purchase #7	$152.85	6.551%	$162.8632	$162.86	$162.85	$162.90
7 purchase totals =	$1,123.99		$1,212.0910	$1,212.09	$1,212.05	$1,212.10