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	$210.35	11.489%	$234.5171	$234.52	$234.50	$234.50
Purchase #2	$190.60	5.231%	$200.5703	$200.57	$200.55	$200.60
Purchase #3	$17.90	10.616%	$19.8003	$19.80	$19.80	$19.80
Purchase #4	$210.37	6.458%	$223.9557	$223.96	$223.95	$224.00
Purchase #5	$85.56	10.648%	$94.6704	$94.67	$94.65	$94.70
Purchase #6	$95.85	4.253%	$99.9265	$99.93	$99.95	$99.90
Purchase #7	$230.32	11.828%	$257.5622	$257.56	$257.55	$257.60
7 purchase totals =	$1,040.95		$1,131.0025	$1,131.01	$1,130.95	$1,131.10