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	$55.60	11.345%	$61.9078	$61.91	$61.90	$61.90
Purchase #2	$236.69	8.112%	$255.8903	$255.89	$255.90	$255.90
Purchase #3	$107.97	7.738%	$116.3247	$116.32	$116.30	$116.30
Purchase #4	$19.66	10.580%	$21.74	$21.74	$21.75	$21.70
Purchase #5	$242.50	3.861%	$251.8629	$251.86	$251.85	$251.90
Purchase #6	$119.45	10.628%	$132.1451	$132.15	$132.15	$132.10
Purchase #7	$149.57	5.410%	$157.6617	$157.66	$157.65	$157.70
7 purchase totals =	$931.44		$997.5325	$997.53	$997.50	$997.50