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	$118.84	10.801%	$131.6759	$131.68	$131.70	$131.70
Purchase #2	$70.61	3.385%	$73.0001	$73.00	$73.00	$73.00
Purchase #3	$116.82	8.283%	$126.4962	$126.50	$126.50	$126.50
Purchase #4	$34.79	13.619%	$39.5281	$39.53	$39.55	$39.50
Purchase #5	$171.76	11.279%	$191.1328	$191.13	$191.15	$191.10
Purchase #6	$158.46	8.853%	$172.4885	$172.49	$172.50	$172.50
Purchase #7	$191.86	7.446%	$206.1459	$206.15	$206.15	$206.10
7 purchase totals =	$863.14		$940.4675	$940.48	$940.55	$940.40