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	$92.77	5.256%	$97.646	$97.65	$97.65	$97.60
Purchase #2	$28.72	8.650%	$31.2043	$31.20	$31.20	$31.20
Purchase #3	$199.72	10.799%	$221.2878	$221.29	$221.30	$221.30
Purchase #4	$116.42	9.410%	$127.3751	$127.38	$127.40	$127.40
Purchase #5	$39.82	8.117%	$43.0522	$43.05	$43.05	$43.10
Purchase #6	$187.47	12.773%	$211.4155	$211.42	$211.40	$211.40
Purchase #7	$157.89	4.517%	$165.0219	$165.02	$165.00	$165.00
7 purchase totals =	$822.81		$897.0028	$897.01	$897.00	$897.00