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	$67.87	3.413%	$70.1864	$70.19	$70.20	$70.20
Purchase #2	$120.48	4.300%	$125.6606	$125.66	$125.65	$125.70
Purchase #3	$118.83	7.610%	$127.873	$127.87	$127.85	$127.90
Purchase #4	$97.64	13.733%	$111.0489	$111.05	$111.05	$111.00
Purchase #5	$155.58	8.500%	$168.8043	$168.80	$168.80	$168.80
Purchase #6	$85.63	8.214%	$92.6636	$92.66	$92.65	$92.70
Purchase #7	$165.59	3.649%	$171.6324	$171.63	$171.65	$171.60
7 purchase totals =	$811.62		$867.8692	$867.86	$867.85	$867.90