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	$60.67	7.804%	$65.4047	$65.40	$65.40	$65.40
Purchase #2	$141.94	6.692%	$151.4386	$151.44	$151.45	$151.40
Purchase #3	$39.79	9.578%	$43.6011	$43.60	$43.60	$43.60
Purchase #4	$46.64	12.460%	$52.4513	$52.45	$52.45	$52.50
Purchase #5	$172.39	9.301%	$188.424	$188.42	$188.40	$188.40
Purchase #6	$164.46	11.749%	$183.7824	$183.78	$183.80	$183.80
Purchase #7	$44.37	3.266%	$45.8191	$45.82	$45.80	$45.80
7 purchase totals =	$670.26		$730.9212	$730.91	$730.90	$730.90