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	$172.82	11.377%	$192.4817	$192.48	$192.50	$192.50
Purchase #2	$181.87	11.284%	$202.3922	$202.39	$202.40	$202.40
Purchase #3	$72.38	11.244%	$80.5184	$80.52	$80.50	$80.50
Purchase #4	$94.28	11.580%	$105.1976	$105.20	$105.20	$105.20
Purchase #5	$200.49	6.336%	$213.193	$213.19	$213.20	$213.20
Purchase #6	$199.96	11.256%	$222.4675	$222.47	$222.45	$222.50
Purchase #7	$84.94	4.774%	$88.995	$89.00	$89.00	$89.00
7 purchase totals =	$1,006.74		$1,105.2454	$1,105.25	$1,105.25	$1,105.30