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	$195.86	9.570%	$214.6038	$214.60	$214.60	$214.60
Purchase #2	$46.42	5.139%	$48.8055	$48.81	$48.80	$48.80
Purchase #3	$146.90	13.829%	$167.2148	$167.21	$167.20	$167.20
Purchase #4	$38.89	11.802%	$43.4798	$43.48	$43.50	$43.50
Purchase #5	$178.89	3.586%	$185.305	$185.31	$185.30	$185.30
Purchase #6	$106.67	13.266%	$120.8208	$120.82	$120.80	$120.80
Purchase #7	$63.39	13.840%	$72.1632	$72.16	$72.15	$72.20
7 purchase totals =	$777.02		$852.3929	$852.39	$852.35	$852.40