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	$137.95	10.436%	$152.3465	$152.35	$152.35	$152.30
Purchase #2	$126.76	12.223%	$142.2539	$142.25	$142.25	$142.30
Purchase #3	$168.56	5.779%	$178.3011	$178.30	$178.30	$178.30
Purchase #4	$156.89	3.206%	$161.9199	$161.92	$161.90	$161.90
Purchase #5	$181.79	4.778%	$190.4759	$190.48	$190.50	$190.50
Purchase #6	$132.98	5.155%	$139.8351	$139.84	$139.85	$139.80
Purchase #7	$199.32	8.178%	$215.6204	$215.62	$215.60	$215.60
7 purchase totals =	$1,104.25		$1,180.7528	$1,180.76	$1,180.75	$1,180.70