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	$122.82	3.706%	$127.3717	$127.37	$127.35	$127.40
Purchase #2	$182.61	9.258%	$199.516	$199.52	$199.50	$199.50
Purchase #3	$121.73	4.211%	$126.8561	$126.86	$126.85	$126.90
Purchase #4	$201.72	5.619%	$213.0546	$213.05	$213.05	$213.10
Purchase #5	$249.37	7.282%	$267.5291	$267.53	$267.55	$267.50
Purchase #6	$162.33	3.480%	$167.9791	$167.98	$168.00	$168.00
Purchase #7	$63.29	5.136%	$66.5406	$66.54	$66.55	$66.50
7 purchase totals =	$1,103.87		$1,168.8472	$1,168.85	$1,168.85	$1,168.90