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	$249.42	10.511%	$275.6365	$275.64	$275.65	$275.60
Purchase #2	$179.63	7.161%	$192.4933	$192.49	$192.50	$192.50
Purchase #3	$143.75	7.747%	$154.8863	$154.89	$154.90	$154.90
Purchase #4	$224.79	4.477%	$234.8538	$234.85	$234.85	$234.90
Purchase #5	$53.83	13.656%	$61.181	$61.18	$61.20	$61.20
Purchase #6	$130.42	8.527%	$141.5409	$141.54	$141.55	$141.50
Purchase #7	$170.88	9.593%	$187.2725	$187.27	$187.25	$187.30
7 purchase totals =	$1,152.72		$1,247.8643	$1,247.86	$1,247.90	$1,247.90