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	$95.60	4.863%	$100.249	$100.25	$100.25	$100.20
Purchase #2	$97.47	12.748%	$109.8955	$109.90	$109.90	$109.90
Purchase #3	$82.46	7.695%	$88.8053	$88.81	$88.80	$88.80
Purchase #4	$23.55	8.698%	$25.5984	$25.60	$25.60	$25.60
Purchase #5	$68.39	5.757%	$72.3272	$72.33	$72.35	$72.30
Purchase #6	$241.44	7.678%	$259.9778	$259.98	$260.00	$260.00
Purchase #7	$56.86	3.513%	$58.8575	$58.86	$58.85	$58.90
7 purchase totals =	$665.77		$715.7107	$715.73	$715.75	$715.70