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	$78.94	6.213%	$83.8445	$83.84	$83.85	$83.80
Purchase #2	$134.96	3.483%	$139.6607	$139.66	$139.65	$139.70
Purchase #3	$212.78	13.568%	$241.65	$241.65	$241.65	$241.70
Purchase #4	$196.69	10.507%	$217.3562	$217.36	$217.35	$217.40
Purchase #5	$53.43	6.599%	$56.9558	$56.96	$56.95	$57.00
Purchase #6	$74.92	13.794%	$85.2545	$85.25	$85.25	$85.30
Purchase #7	$205.80	12.466%	$231.455	$231.46	$231.45	$231.50
7 purchase totals =	$957.52		$1,056.1767	$1,056.18	$1,056.15	$1,056.40