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	$182.27	7.667%	$196.2446	$196.24	$196.25	$196.20
Purchase #2	$95.85	12.560%	$107.8888	$107.89	$107.90	$107.90
Purchase #3	$222.37	3.396%	$229.9217	$229.92	$229.90	$229.90
Purchase #4	$50.57	9.645%	$55.4475	$55.45	$55.45	$55.40
Purchase #5	$130.86	9.437%	$143.2093	$143.21	$143.20	$143.20
Purchase #6	$31.78	12.220%	$35.6635	$35.66	$35.65	$35.70
Purchase #7	$122.83	4.629%	$128.5158	$128.52	$128.50	$128.50
7 purchase totals =	$836.53		$896.8912	$896.89	$896.85	$896.80