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	$53.92	10.427%	$59.5422	$59.54	$59.55	$59.50
Purchase #2	$148.55	13.659%	$168.8404	$168.84	$168.85	$168.80
Purchase #3	$24.80	10.678%	$27.4481	$27.45	$27.45	$27.40
Purchase #4	$119.56	10.870%	$132.5562	$132.56	$132.55	$132.60
Purchase #5	$212.26	12.841%	$239.5163	$239.52	$239.50	$239.50
Purchase #6	$9.25	13.631%	$10.5109	$10.51	$10.50	$10.50
Purchase #7	$163.61	6.519%	$174.2757	$174.28	$174.30	$174.30
7 purchase totals =	$731.95		$812.6898	$812.70	$812.70	$812.60