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	$56.91	10.249%	$62.7427	$62.74	$62.75	$62.70
Purchase #2	$22.46	5.618%	$23.7218	$23.72	$23.70	$23.70
Purchase #3	$157.37	8.742%	$171.1273	$171.13	$171.15	$171.10
Purchase #4	$35.52	4.576%	$37.1454	$37.15	$37.15	$37.10
Purchase #5	$17.72	11.851%	$19.82	$19.82	$19.80	$19.80
Purchase #6	$105.72	10.181%	$116.4834	$116.48	$116.50	$116.50
Purchase #7	$25.83	5.349%	$27.2116	$27.21	$27.20	$27.20
7 purchase totals =	$421.53		$458.2522	$458.25	$458.25	$458.10