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	$10.95	10.267%	$12.0742	$12.07	$12.05	$12.10
Purchase #2	$40.34	6.216%	$42.8475	$42.85	$42.85	$42.80
Purchase #3	$120.31	6.831%	$128.5284	$128.53	$128.55	$128.50
Purchase #4	$86.96	8.297%	$94.1751	$94.18	$94.20	$94.20
Purchase #5	$157.59	8.828%	$171.502	$171.50	$171.50	$171.50
Purchase #6	$71.88	13.394%	$81.5076	$81.51	$81.50	$81.50
Purchase #7	$207.29	7.291%	$222.4035	$222.40	$222.40	$222.40
7 purchase totals =	$695.32		$753.0383	$753.04	$753.05	$753.00