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	$56.40	5.373%	$59.4304	$59.43	$59.45	$59.40
Purchase #2	$187.60	10.811%	$207.8814	$207.88	$207.90	$207.90
Purchase #3	$33.43	4.297%	$34.8665	$34.87	$34.85	$34.90
Purchase #4	$82.54	12.187%	$92.5991	$92.60	$92.60	$92.60
Purchase #5	$211.87	5.598%	$223.7305	$223.73	$223.75	$223.70
Purchase #6	$87.33	12.232%	$98.0122	$98.01	$98.00	$98.00
Purchase #7	$141.83	3.874%	$147.3245	$147.32	$147.30	$147.30
7 purchase totals =	$801.00		$863.8446	$863.84	$863.85	$863.80