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	$241.99	7.256%	$259.5488	$259.55	$259.55	$259.50
Purchase #2	$78.53	12.861%	$88.6297	$88.63	$88.65	$88.60
Purchase #3	$173.80	5.254%	$182.9315	$182.93	$182.95	$182.90
Purchase #4	$220.28	5.119%	$231.5561	$231.56	$231.55	$231.60
Purchase #5	$31.56	5.686%	$33.3545	$33.35	$33.35	$33.40
Purchase #6	$125.45	11.549%	$139.9382	$139.94	$139.95	$139.90
Purchase #7	$90.64	10.530%	$100.1844	$100.18	$100.20	$100.20
7 purchase totals =	$962.25		$1,036.1432	$1,036.14	$1,036.20	$1,036.10