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	$192.94	3.641%	$199.9649	$199.96	$199.95	$200.00
Purchase #2	$32.55	8.383%	$35.2787	$35.28	$35.30	$35.30
Purchase #3	$101.84	9.753%	$111.7725	$111.77	$111.75	$111.80
Purchase #4	$152.60	9.767%	$167.5044	$167.50	$167.50	$167.50
Purchase #5	$120.50	7.105%	$129.0615	$129.06	$129.05	$129.10
Purchase #6	$66.96	5.233%	$70.464	$70.46	$70.45	$70.50
Purchase #7	$93.41	7.235%	$100.1682	$100.17	$100.15	$100.20
7 purchase totals =	$760.80		$814.2142	$814.20	$814.15	$814.40