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	$87.47	4.762%	$91.6353	$91.64	$91.65	$91.60
Purchase #2	$118.66	10.648%	$131.2949	$131.29	$131.30	$131.30
Purchase #3	$250.97	10.264%	$276.7296	$276.73	$276.75	$276.70
Purchase #4	$247.64	11.689%	$276.5866	$276.59	$276.60	$276.60
Purchase #5	$151.88	13.804%	$172.8455	$172.85	$172.85	$172.80
Purchase #6	$55.68	8.193%	$60.2419	$60.24	$60.25	$60.20
Purchase #7	$82.86	9.341%	$90.6	$90.60	$90.60	$90.60
7 purchase totals =	$995.16		$1,099.9338	$1,099.94	$1,100.00	$1,099.80