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	$82.65	3.417%	$85.4742	$85.47	$85.45	$85.50
Purchase #2	$82.68	3.334%	$85.4366	$85.44	$85.45	$85.40
Purchase #3	$36.47	9.423%	$39.9066	$39.91	$39.90	$39.90
Purchase #4	$169.95	6.305%	$180.6653	$180.67	$180.65	$180.70
Purchase #5	$70.51	4.188%	$73.463	$73.46	$73.45	$73.50
Purchase #6	$86.56	6.291%	$92.0055	$92.01	$92.00	$92.00
Purchase #7	$114.86	10.790%	$127.2534	$127.25	$127.25	$127.30
7 purchase totals =	$643.68		$684.2046	$684.21	$684.15	$684.30