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	$169.89	10.868%	$188.3536	$188.35	$188.35	$188.40
Purchase #2	$149.96	5.508%	$158.2198	$158.22	$158.20	$158.20
Purchase #3	$104.90	12.345%	$117.8499	$117.85	$117.85	$117.80
Purchase #4	$104.59	7.730%	$112.6748	$112.67	$112.65	$112.70
Purchase #5	$221.97	10.204%	$244.6198	$244.62	$244.60	$244.60
Purchase #6	$43.54	3.642%	$45.1257	$45.13	$45.15	$45.10
Purchase #7	$159.43	13.587%	$181.0918	$181.09	$181.10	$181.10
7 purchase totals =	$954.28		$1,047.9354	$1,047.93	$1,047.90	$1,047.90