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	$59.42	13.821%	$67.6324	$67.63	$67.65	$67.60
Purchase #2	$201.57	4.638%	$210.9188	$210.92	$210.90	$210.90
Purchase #3	$87.59	4.832%	$91.8223	$91.82	$91.80	$91.80
Purchase #4	$229.89	8.704%	$249.8996	$249.90	$249.90	$249.90
Purchase #5	$229.31	7.473%	$246.4463	$246.45	$246.45	$246.40
Purchase #6	$19.71	6.172%	$20.9265	$20.93	$20.95	$20.90
Purchase #7	$178.83	6.532%	$190.5112	$190.51	$190.50	$190.50
7 purchase totals =	$1,006.32		$1,078.1571	$1,078.16	$1,078.15	$1,078.00