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	$155.55	11.329%	$173.1723	$173.17	$173.15	$173.20
Purchase #2	$43.78	11.737%	$48.9185	$48.92	$48.90	$48.90
Purchase #3	$197.34	12.664%	$222.3311	$222.33	$222.35	$222.30
Purchase #4	$38.26	5.750%	$40.46	$40.46	$40.45	$40.50
Purchase #5	$11.40	11.116%	$12.6672	$12.67	$12.65	$12.70
Purchase #6	$117.49	5.663%	$124.1435	$124.14	$124.15	$124.10
Purchase #7	$235.96	3.340%	$243.8411	$243.84	$243.85	$243.80
7 purchase totals =	$799.78		$865.5337	$865.53	$865.50	$865.50