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	$69.83	3.531%	$72.2957	$72.30	$72.30	$72.30
Purchase #2	$95.81	7.438%	$102.9363	$102.94	$102.95	$102.90
Purchase #3	$195.67	13.700%	$222.4768	$222.48	$222.50	$222.50
Purchase #4	$99.49	13.668%	$113.0883	$113.09	$113.10	$113.10
Purchase #5	$199.93	13.830%	$227.5803	$227.58	$227.60	$227.60
Purchase #6	$195.77	12.680%	$220.5936	$220.59	$220.60	$220.60
Purchase #7	$83.86	10.399%	$92.5806	$92.58	$92.60	$92.60
7 purchase totals =	$940.36		$1,051.5516	$1,051.56	$1,051.65	$1,051.60