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	$84.37	7.651%	$90.8251	$90.83	$90.85	$90.80
Purchase #2	$129.60	7.714%	$139.5973	$139.60	$139.60	$139.60
Purchase #3	$14.30	13.430%	$16.2205	$16.22	$16.20	$16.20
Purchase #4	$74.34	4.188%	$77.4534	$77.45	$77.45	$77.50
Purchase #5	$99.34	11.223%	$110.4889	$110.49	$110.50	$110.50
Purchase #6	$78.59	8.239%	$85.065	$85.07	$85.05	$85.10
Purchase #7	$94.66	5.647%	$100.0055	$100.01	$100.00	$100.00
7 purchase totals =	$575.20		$619.6557	$619.67	$619.65	$619.70