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	$99.64	9.703%	$109.3081	$109.31	$109.30	$109.30
Purchase #2	$212.32	10.591%	$234.8068	$234.81	$234.80	$234.80
Purchase #3	$67.47	4.367%	$70.4164	$70.42	$70.40	$70.40
Purchase #4	$231.57	3.162%	$238.8922	$238.89	$238.90	$238.90
Purchase #5	$161.72	4.786%	$169.4599	$169.46	$169.45	$169.50
Purchase #6	$199.37	11.677%	$222.6504	$222.65	$222.65	$222.70
Purchase #7	$236.77	8.271%	$256.3532	$256.35	$256.35	$256.40
7 purchase totals =	$1,208.86		$1,301.8870	$1,301.89	$1,301.85	$1,302.00