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	$243.88	3.560%	$252.5621	$252.56	$252.55	$252.60
Purchase #2	$30.43	11.342%	$33.8814	$33.88	$33.90	$33.90
Purchase #3	$36.66	9.172%	$40.0225	$40.02	$40.00	$40.00
Purchase #4	$149.35	10.770%	$165.435	$165.44	$165.45	$165.40
Purchase #5	$71.30	9.518%	$78.0863	$78.09	$78.10	$78.10
Purchase #6	$211.83	5.237%	$222.9235	$222.92	$222.90	$222.90
Purchase #7	$98.25	4.118%	$102.2959	$102.30	$102.30	$102.30
7 purchase totals =	$841.70		$895.2067	$895.21	$895.20	$895.20