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	$119.98	9.855%	$131.804	$131.80	$131.80	$131.80
Purchase #2	$43.61	4.802%	$45.7042	$45.70	$45.70	$45.70
Purchase #3	$231.86	5.635%	$244.9253	$244.93	$244.95	$244.90
Purchase #4	$75.45	3.702%	$78.2432	$78.24	$78.25	$78.20
Purchase #5	$99.61	13.735%	$113.2914	$113.29	$113.30	$113.30
Purchase #6	$112.49	4.382%	$117.4193	$117.42	$117.40	$117.40
Purchase #7	$28.69	11.756%	$32.0628	$32.06	$32.05	$32.10
7 purchase totals =	$711.69		$763.4502	$763.44	$763.45	$763.40