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	$73.59	3.285%	$76.0074	$76.01	$76.00	$76.00
Purchase #2	$200.45	6.651%	$213.7819	$213.78	$213.80	$213.80
Purchase #3	$67.66	6.669%	$72.1722	$72.17	$72.15	$72.20
Purchase #4	$224.96	4.149%	$234.2936	$234.29	$234.30	$234.30
Purchase #5	$143.38	11.116%	$159.3181	$159.32	$159.30	$159.30
Purchase #6	$35.89	9.124%	$39.1646	$39.16	$39.15	$39.20
Purchase #7	$234.76	3.156%	$242.169	$242.17	$242.15	$242.20
7 purchase totals =	$980.69		$1,036.9068	$1,036.90	$1,036.85	$1,037.00