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	$53.45	8.193%	$57.8292	$57.83	$57.85	$57.80
Purchase #2	$156.95	13.484%	$178.1131	$178.11	$178.10	$178.10
Purchase #3	$160.47	7.226%	$172.0656	$172.07	$172.05	$172.10
Purchase #4	$249.95	3.569%	$258.8707	$258.87	$258.85	$258.90
Purchase #5	$59.63	3.689%	$61.8298	$61.83	$61.85	$61.80
Purchase #6	$130.41	3.494%	$134.9665	$134.97	$134.95	$135.00
Purchase #7	$197.72	12.825%	$223.0776	$223.08	$223.10	$223.10
7 purchase totals =	$1,008.58		$1,086.7525	$1,086.76	$1,086.75	$1,086.80