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	$218.71	7.660%	$235.4632	$235.46	$235.45	$235.50
Purchase #2	$42.32	7.736%	$45.5939	$45.59	$45.60	$45.60
Purchase #3	$71.96	9.353%	$78.6904	$78.69	$78.70	$78.70
Purchase #4	$8.52	3.559%	$8.8232	$8.82	$8.80	$8.80
Purchase #5	$24.44	12.461%	$27.4855	$27.49	$27.50	$27.50
Purchase #6	$197.69	7.635%	$212.7836	$212.78	$212.80	$212.80
Purchase #7	$88.40	13.339%	$100.1917	$100.19	$100.20	$100.20
7 purchase totals =	$652.04		$709.0315	$709.02	$709.05	$709.10