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	$104.84	11.648%	$117.0518	$117.05	$117.05	$117.10
Purchase #2	$48.62	6.210%	$51.6393	$51.64	$51.65	$51.60
Purchase #3	$99.52	4.619%	$104.1168	$104.12	$104.10	$104.10
Purchase #4	$166.39	9.324%	$181.9042	$181.90	$181.90	$181.90
Purchase #5	$137.47	7.265%	$147.4572	$147.46	$147.45	$147.50
Purchase #6	$45.60	6.310%	$48.4774	$48.48	$48.50	$48.50
Purchase #7	$133.59	11.457%	$148.8954	$148.90	$148.90	$148.90
7 purchase totals =	$736.03		$799.5421	$799.55	$799.55	$799.60