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	$131.76	9.646%	$144.4696	$144.47	$144.45	$144.50
Purchase #2	$31.96	4.214%	$33.3068	$33.31	$33.30	$33.30
Purchase #3	$184.25	4.105%	$191.8135	$191.81	$191.80	$191.80
Purchase #4	$31.76	6.597%	$33.8552	$33.86	$33.85	$33.90
Purchase #5	$85.57	7.635%	$92.1033	$92.10	$92.10	$92.10
Purchase #6	$27.76	8.181%	$30.031	$30.03	$30.05	$30.00
Purchase #7	$151.59	6.795%	$161.8905	$161.89	$161.90	$161.90
7 purchase totals =	$644.65		$687.4699	$687.47	$687.45	$687.50