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	$95.27	4.406%	$99.4676	$99.47	$99.45	$99.50
Purchase #2	$159.39	3.125%	$164.3709	$164.37	$164.35	$164.40
Purchase #3	$82.80	10.527%	$91.5164	$91.52	$91.50	$91.50
Purchase #4	$96.37	11.811%	$107.7523	$107.75	$107.75	$107.80
Purchase #5	$30.40	7.294%	$32.6174	$32.62	$32.60	$32.60
Purchase #6	$109.61	12.756%	$123.5919	$123.59	$123.60	$123.60
Purchase #7	$120.39	9.212%	$131.4803	$131.48	$131.50	$131.50
7 purchase totals =	$694.23		$750.7968	$750.80	$750.75	$750.90