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	$6.47	7.159%	$6.9332	$6.93	$6.95	$6.90
Purchase #2	$85.66	11.605%	$95.6008	$95.60	$95.60	$95.60
Purchase #3	$190.30	10.489%	$210.2606	$210.26	$210.25	$210.30
Purchase #4	$164.75	11.323%	$183.4046	$183.40	$183.40	$183.40
Purchase #5	$103.74	7.352%	$111.367	$111.37	$111.35	$111.40
Purchase #6	$105.99	5.180%	$111.4803	$111.48	$111.50	$111.50
Purchase #7	$59.34	13.172%	$67.1563	$67.16	$67.15	$67.20
7 purchase totals =	$716.25		$786.2028	$786.20	$786.20	$786.30