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	$112.78	3.351%	$116.5593	$116.56	$116.55	$116.60
Purchase #2	$213.59	4.653%	$223.5283	$223.53	$223.55	$223.50
Purchase #3	$129.56	11.472%	$144.4231	$144.42	$144.40	$144.40
Purchase #4	$157.67	11.669%	$176.0685	$176.07	$176.05	$176.10
Purchase #5	$132.28	7.858%	$142.6746	$142.67	$142.65	$142.70
Purchase #6	$56.59	5.242%	$59.5564	$59.56	$59.55	$59.60
Purchase #7	$34.42	13.780%	$39.1631	$39.16	$39.15	$39.20
7 purchase totals =	$836.89		$901.9733	$901.97	$901.90	$902.10