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	$234.72	11.417%	$261.518	$261.52	$261.50	$261.50
Purchase #2	$225.31	13.520%	$255.7719	$255.77	$255.75	$255.80
Purchase #3	$63.60	10.540%	$70.3034	$70.30	$70.30	$70.30
Purchase #4	$107.33	13.562%	$121.8861	$121.89	$121.90	$121.90
Purchase #5	$137.39	5.428%	$144.8475	$144.85	$144.85	$144.80
Purchase #6	$26.61	3.557%	$27.5565	$27.56	$27.55	$27.60
Purchase #7	$112.66	13.626%	$128.0111	$128.01	$128.00	$128.00
7 purchase totals =	$907.62		$1,009.8945	$1,009.90	$1,009.85	$1,009.90