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	$68.58	11.575%	$76.5181	$76.52	$76.50	$76.50
Purchase #2	$184.32	5.338%	$194.159	$194.16	$194.15	$194.20
Purchase #3	$136.34	6.604%	$145.3439	$145.34	$145.35	$145.30
Purchase #4	$41.73	9.687%	$45.7724	$45.77	$45.75	$45.80
Purchase #5	$37.28	10.709%	$41.2723	$41.27	$41.25	$41.30
Purchase #6	$200.78	4.539%	$209.8934	$209.89	$209.90	$209.90
Purchase #7	$12.97	7.546%	$13.9487	$13.95	$13.95	$13.90
7 purchase totals =	$682.00		$726.9078	$726.90	$726.85	$726.90