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	$62.77	8.199%	$67.9165	$67.92	$67.90	$67.90
Purchase #2	$232.89	6.249%	$247.4433	$247.44	$247.45	$247.40
Purchase #3	$141.90	13.266%	$160.7245	$160.72	$160.70	$160.70
Purchase #4	$222.96	6.742%	$237.992	$237.99	$238.00	$238.00
Purchase #5	$158.38	10.396%	$174.8452	$174.85	$174.85	$174.80
Purchase #6	$161.57	11.346%	$179.9017	$179.90	$179.90	$179.90
Purchase #7	$121.49	8.397%	$131.6915	$131.69	$131.70	$131.70
7 purchase totals =	$1,101.96		$1,200.5147	$1,200.51	$1,200.50	$1,200.40