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	$72.31	7.263%	$77.5619	$77.56	$77.55	$77.60
Purchase #2	$208.32	6.769%	$222.4212	$222.42	$222.40	$222.40
Purchase #3	$98.27	13.636%	$111.6701	$111.67	$111.65	$111.70
Purchase #4	$25.83	12.537%	$29.0683	$29.07	$29.05	$29.10
Purchase #5	$76.76	7.689%	$82.6621	$82.66	$82.65	$82.70
Purchase #6	$131.50	7.835%	$141.803	$141.80	$141.80	$141.80
Purchase #7	$66.45	12.617%	$74.834	$74.83	$74.85	$74.80
7 purchase totals =	$679.44		$740.0206	$740.01	$739.95	$740.10