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	$228.61	13.775%	$260.101	$260.10	$260.10	$260.10
Purchase #2	$192.83	4.485%	$201.4784	$201.48	$201.50	$201.50
Purchase #3	$147.87	13.868%	$168.3766	$168.38	$168.40	$168.40
Purchase #4	$141.35	7.643%	$152.1534	$152.15	$152.15	$152.20
Purchase #5	$96.97	8.469%	$105.1824	$105.18	$105.20	$105.20
Purchase #6	$156.43	5.409%	$164.8913	$164.89	$164.90	$164.90
Purchase #7	$30.88	11.397%	$34.3994	$34.40	$34.40	$34.40
7 purchase totals =	$994.94		$1,086.5825	$1,086.58	$1,086.65	$1,086.70