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	$71.43	9.136%	$77.9558	$77.96	$77.95	$78.00
Purchase #2	$26.36	3.530%	$27.2905	$27.29	$27.30	$27.30
Purchase #3	$89.75	3.433%	$92.8311	$92.83	$92.85	$92.80
Purchase #4	$13.70	12.327%	$15.3888	$15.39	$15.40	$15.40
Purchase #5	$20.29	11.119%	$22.546	$22.55	$22.55	$22.50
Purchase #6	$174.29	13.839%	$198.41	$198.41	$198.40	$198.40
Purchase #7	$158.61	8.467%	$172.0395	$172.04	$172.05	$172.00
7 purchase totals =	$554.43		$606.4617	$606.47	$606.50	$606.40