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	$30.98	6.360%	$32.9503	$32.95	$32.95	$33.00
Purchase #2	$59.81	13.182%	$67.6942	$67.69	$67.70	$67.70
Purchase #3	$224.75	7.210%	$240.9545	$240.95	$240.95	$241.00
Purchase #4	$20.87	4.868%	$21.886	$21.89	$21.90	$21.90
Purchase #5	$124.26	3.128%	$128.1469	$128.15	$128.15	$128.10
Purchase #6	$105.47	10.440%	$116.4811	$116.48	$116.50	$116.50
Purchase #7	$204.68	11.609%	$228.4413	$228.44	$228.45	$228.40
7 purchase totals =	$770.82		$836.5543	$836.55	$836.60	$836.60