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	$113.70	4.666%	$119.0052	$119.01	$119.00	$119.00
Purchase #2	$38.47	13.446%	$43.6427	$43.64	$43.65	$43.60
Purchase #3	$64.87	12.744%	$73.137	$73.14	$73.15	$73.10
Purchase #4	$122.64	13.772%	$139.53	$139.53	$139.55	$139.50
Purchase #5	$74.65	9.720%	$81.906	$81.91	$81.90	$81.90
Purchase #6	$228.25	13.732%	$259.5933	$259.59	$259.60	$259.60
Purchase #7	$79.79	13.473%	$90.5401	$90.54	$90.55	$90.50
7 purchase totals =	$722.37		$807.3543	$807.36	$807.40	$807.20