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	$56.91	7.294%	$61.061	$61.06	$61.05	$61.10
Purchase #2	$148.26	9.585%	$162.4707	$162.47	$162.45	$162.50
Purchase #3	$204.34	6.639%	$217.9061	$217.91	$217.90	$217.90
Purchase #4	$80.58	3.481%	$83.385	$83.39	$83.40	$83.40
Purchase #5	$90.48	10.459%	$99.9433	$99.94	$99.95	$99.90
Purchase #6	$176.25	9.434%	$192.8774	$192.88	$192.90	$192.90
Purchase #7	$78.60	6.776%	$83.9259	$83.93	$83.95	$83.90
7 purchase totals =	$835.42		$901.5694	$901.58	$901.60	$901.60