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	$242.53	7.791%	$261.4255	$261.43	$261.45	$261.40
Purchase #2	$86.91	4.635%	$90.9383	$90.94	$90.95	$90.90
Purchase #3	$140.51	8.566%	$152.5461	$152.55	$152.55	$152.50
Purchase #4	$241.64	6.365%	$257.0204	$257.02	$257.00	$257.00
Purchase #5	$141.55	6.320%	$150.496	$150.50	$150.50	$150.50
Purchase #6	$160.42	11.815%	$179.3736	$179.37	$179.35	$179.40
Purchase #7	$128.52	9.542%	$140.7834	$140.78	$140.80	$140.80
7 purchase totals =	$1,142.08		$1,232.5833	$1,232.59	$1,232.60	$1,232.50