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	$5.42	3.382%	$5.6033	$5.60	$5.60	$5.60
Purchase #2	$103.91	8.807%	$113.0614	$113.06	$113.05	$113.10
Purchase #3	$98.26	13.388%	$111.415	$111.42	$111.40	$111.40
Purchase #4	$17.91	9.355%	$19.5855	$19.59	$19.60	$19.60
Purchase #5	$85.72	7.192%	$91.885	$91.89	$91.90	$91.90
Purchase #6	$208.74	11.386%	$232.5071	$232.51	$232.50	$232.50
Purchase #7	$131.79	5.307%	$138.7841	$138.78	$138.80	$138.80
7 purchase totals =	$651.75		$712.8414	$712.85	$712.85	$712.90