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	$229.36	5.443%	$241.8441	$241.84	$241.85	$241.80
Purchase #2	$80.96	10.730%	$89.647	$89.65	$89.65	$89.60
Purchase #3	$168.46	11.276%	$187.4555	$187.46	$187.45	$187.50
Purchase #4	$231.65	4.422%	$241.8936	$241.89	$241.90	$241.90
Purchase #5	$32.26	10.345%	$35.5973	$35.60	$35.60	$35.60
Purchase #6	$151.39	6.591%	$161.3681	$161.37	$161.35	$161.40
Purchase #7	$190.38	8.692%	$206.9278	$206.93	$206.95	$206.90
7 purchase totals =	$1,084.46		$1,164.7334	$1,164.74	$1,164.75	$1,164.70