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	$90.61	5.742%	$95.8128	$95.81	$95.80	$95.80
Purchase #2	$31.25	10.340%	$34.4813	$34.48	$34.50	$34.50
Purchase #3	$18.79	6.584%	$20.0271	$20.03	$20.05	$20.00
Purchase #4	$196.85	9.494%	$215.5389	$215.54	$215.55	$215.50
Purchase #5	$64.50	5.627%	$68.1294	$68.13	$68.15	$68.10
Purchase #6	$157.26	3.314%	$162.4716	$162.47	$162.45	$162.50
Purchase #7	$78.89	7.835%	$85.071	$85.07	$85.05	$85.10
7 purchase totals =	$638.15		$681.5321	$681.53	$681.55	$681.50