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	$187.83	6.163%	$199.406	$199.41	$199.40	$199.40
Purchase #2	$238.90	9.410%	$261.3805	$261.38	$261.40	$261.40
Purchase #3	$184.83	13.524%	$209.8264	$209.83	$209.85	$209.80
Purchase #4	$25.39	9.744%	$27.864	$27.86	$27.85	$27.90
Purchase #5	$90.63	13.495%	$102.8605	$102.86	$102.85	$102.90
Purchase #6	$11.39	11.180%	$12.6634	$12.66	$12.65	$12.70
Purchase #7	$103.45	7.873%	$111.5946	$111.59	$111.60	$111.60
7 purchase totals =	$842.42		$925.5954	$925.59	$925.60	$925.70