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	$160.82	9.473%	$176.0545	$176.05	$176.05	$176.10
Purchase #2	$162.53	7.774%	$175.1651	$175.17	$175.15	$175.20
Purchase #3	$84.93	4.237%	$88.5285	$88.53	$88.55	$88.50
Purchase #4	$155.67	11.668%	$173.8336	$173.83	$173.85	$173.80
Purchase #5	$75.31	4.314%	$78.5589	$78.56	$78.55	$78.60
Purchase #6	$66.95	8.106%	$72.377	$72.38	$72.40	$72.40
Purchase #7	$35.96	4.118%	$37.4408	$37.44	$37.45	$37.40
7 purchase totals =	$742.17		$801.9584	$801.96	$802.00	$802.00