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	$93.64	12.676%	$105.5098	$105.51	$105.50	$105.50
Purchase #2	$40.72	7.507%	$43.7769	$43.78	$43.80	$43.80
Purchase #3	$220.43	9.465%	$241.2937	$241.29	$241.30	$241.30
Purchase #4	$232.56	12.352%	$261.2858	$261.29	$261.30	$261.30
Purchase #5	$127.78	7.269%	$137.0683	$137.07	$137.05	$137.10
Purchase #6	$123.75	7.846%	$133.4594	$133.46	$133.45	$133.50
Purchase #7	$244.74	5.194%	$257.4518	$257.45	$257.45	$257.50
7 purchase totals =	$1,083.62		$1,179.8457	$1,179.85	$1,179.85	$1,180.00