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	$191.71	4.573%	$200.4769	$200.48	$200.50	$200.50
Purchase #2	$239.75	13.605%	$272.368	$272.37	$272.35	$272.40
Purchase #3	$249.38	10.239%	$274.914	$274.91	$274.90	$274.90
Purchase #4	$51.35	11.839%	$57.4293	$57.43	$57.45	$57.40
Purchase #5	$18.40	9.197%	$20.0922	$20.09	$20.10	$20.10
Purchase #6	$93.41	7.574%	$100.4849	$100.48	$100.50	$100.50
Purchase #7	$100.62	9.372%	$110.0501	$110.05	$110.05	$110.10
7 purchase totals =	$944.62		$1,035.8154	$1,035.81	$1,035.85	$1,035.90