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	$250.66	4.683%	$262.3984	$262.40	$262.40	$262.40
Purchase #2	$79.78	8.362%	$86.4512	$86.45	$86.45	$86.50
Purchase #3	$195.93	5.783%	$207.2606	$207.26	$207.25	$207.30
Purchase #4	$200.38	8.741%	$217.8952	$217.90	$217.90	$217.90
Purchase #5	$143.93	10.849%	$159.545	$159.55	$159.55	$159.50
Purchase #6	$61.57	9.552%	$67.4512	$67.45	$67.45	$67.50
Purchase #7	$196.78	7.172%	$210.8931	$210.89	$210.90	$210.90
7 purchase totals =	$1,129.03		$1,211.8947	$1,211.90	$1,211.90	$1,212.00