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	$94.79	8.456%	$102.8054	$102.81	$102.80	$102.80
Purchase #2	$135.70	7.673%	$146.1123	$146.11	$146.10	$146.10
Purchase #3	$176.56	7.389%	$189.606	$189.61	$189.60	$189.60
Purchase #4	$230.88	5.437%	$243.4329	$243.43	$243.45	$243.40
Purchase #5	$48.29	3.454%	$49.9579	$49.96	$49.95	$50.00
Purchase #6	$171.50	11.726%	$191.6101	$191.61	$191.60	$191.60
Purchase #7	$167.84	5.338%	$176.7993	$176.80	$176.80	$176.80
7 purchase totals =	$1,025.56		$1,100.3239	$1,100.33	$1,100.30	$1,100.30