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	$248.67	4.480%	$259.8104	$259.81	$259.80	$259.80
Purchase #2	$124.69	11.743%	$139.3323	$139.33	$139.35	$139.30
Purchase #3	$28.57	9.384%	$31.251	$31.25	$31.25	$31.30
Purchase #4	$176.78	7.545%	$190.1181	$190.12	$190.10	$190.10
Purchase #5	$55.27	13.551%	$62.7596	$62.76	$62.75	$62.80
Purchase #6	$42.67	4.342%	$44.5227	$44.52	$44.50	$44.50
Purchase #7	$172.63	12.397%	$194.0309	$194.03	$194.05	$194.00
7 purchase totals =	$849.28		$921.8250	$921.82	$921.80	$921.80