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	$45.76	4.569%	$47.8508	$47.85	$47.85	$47.90
Purchase #2	$97.78	4.168%	$101.8555	$101.86	$101.85	$101.90
Purchase #3	$169.83	6.255%	$180.4529	$180.45	$180.45	$180.50
Purchase #4	$161.39	3.209%	$166.569	$166.57	$166.55	$166.60
Purchase #5	$229.61	12.317%	$257.8911	$257.89	$257.90	$257.90
Purchase #6	$42.98	12.709%	$48.4423	$48.44	$48.45	$48.40
Purchase #7	$147.25	8.177%	$159.2906	$159.29	$159.30	$159.30
7 purchase totals =	$894.60		$962.3522	$962.35	$962.35	$962.50