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	$54.64	9.558%	$59.8625	$59.86	$59.85	$59.90
Purchase #2	$217.67	12.718%	$245.3533	$245.35	$245.35	$245.40
Purchase #3	$54.75	3.147%	$56.473	$56.47	$56.45	$56.50
Purchase #4	$20.92	4.505%	$21.8624	$21.86	$21.85	$21.90
Purchase #5	$74.91	13.623%	$85.115	$85.12	$85.10	$85.10
Purchase #6	$171.54	8.403%	$185.9545	$185.95	$185.95	$186.00
Purchase #7	$87.93	4.832%	$92.1788	$92.18	$92.20	$92.20
7 purchase totals =	$682.36		$746.7995	$746.79	$746.75	$747.00