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	$31.88	6.541%	$33.9653	$33.97	$33.95	$34.00
Purchase #2	$134.30	3.794%	$139.3953	$139.40	$139.40	$139.40
Purchase #3	$50.76	4.678%	$53.1346	$53.13	$53.15	$53.10
Purchase #4	$186.25	7.638%	$200.4758	$200.48	$200.50	$200.50
Purchase #5	$57.45	6.352%	$61.0992	$61.10	$61.10	$61.10
Purchase #6	$154.75	10.826%	$171.5032	$171.50	$171.50	$171.50
Purchase #7	$215.29	8.410%	$233.3959	$233.40	$233.40	$233.40
7 purchase totals =	$830.68		$892.9693	$892.98	$893.00	$893.00