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	$222.31	4.741%	$232.8497	$232.85	$232.85	$232.80
Purchase #2	$117.91	11.371%	$131.3175	$131.32	$131.30	$131.30
Purchase #3	$132.49	6.749%	$141.4318	$141.43	$141.45	$141.40
Purchase #4	$70.32	11.175%	$78.1783	$78.18	$78.20	$78.20
Purchase #5	$171.26	11.548%	$191.0371	$191.04	$191.05	$191.00
Purchase #6	$71.27	4.168%	$74.2405	$74.24	$74.25	$74.20
Purchase #7	$164.90	13.739%	$187.5556	$187.56	$187.55	$187.60
7 purchase totals =	$950.46		$1,036.6105	$1,036.62	$1,036.65	$1,036.50