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	$80.47	9.181%	$87.858	$87.86	$87.85	$87.90
Purchase #2	$42.45	3.401%	$43.8937	$43.89	$43.90	$43.90
Purchase #3	$104.42	6.784%	$111.5039	$111.50	$111.50	$111.50
Purchase #4	$229.63	13.342%	$260.2672	$260.27	$260.25	$260.30
Purchase #5	$199.81	5.556%	$210.9114	$210.91	$210.90	$210.90
Purchase #6	$171.77	10.233%	$189.3472	$189.35	$189.35	$189.30
Purchase #7	$55.77	3.203%	$57.5563	$57.56	$57.55	$57.60
7 purchase totals =	$884.32		$961.3377	$961.34	$961.30	$961.40