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	$73.25	7.307%	$78.6024	$78.60	$78.60	$78.60
Purchase #2	$58.61	8.451%	$63.5631	$63.56	$63.55	$63.60
Purchase #3	$85.55	12.668%	$96.3875	$96.39	$96.40	$96.40
Purchase #4	$161.63	4.320%	$168.6124	$168.61	$168.60	$168.60
Purchase #5	$105.89	11.255%	$117.8079	$117.81	$117.80	$117.80
Purchase #6	$146.30	3.799%	$151.8579	$151.86	$151.85	$151.90
Purchase #7	$119.47	6.277%	$126.9691	$126.97	$126.95	$127.00
7 purchase totals =	$750.70		$803.8003	$803.80	$803.75	$803.90