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	$199.76	7.859%	$215.4591	$215.46	$215.45	$215.50
Purchase #2	$69.54	6.756%	$74.2381	$74.24	$74.25	$74.20
Purchase #3	$134.55	5.192%	$141.5358	$141.54	$141.55	$141.50
Purchase #4	$91.91	3.770%	$95.375	$95.38	$95.40	$95.40
Purchase #5	$61.52	6.430%	$65.4757	$65.48	$65.50	$65.50
Purchase #6	$112.77	12.447%	$126.8065	$126.81	$126.80	$126.80
Purchase #7	$87.81	8.811%	$95.5469	$95.55	$95.55	$95.50
7 purchase totals =	$757.86		$814.4371	$814.46	$814.50	$814.40