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	$118.60	11.241%	$131.9318	$131.93	$131.95	$131.90
Purchase #2	$65.27	9.529%	$71.4896	$71.49	$71.50	$71.50
Purchase #3	$103.44	6.215%	$109.8688	$109.87	$109.85	$109.90
Purchase #4	$87.37	4.534%	$91.3314	$91.33	$91.35	$91.30
Purchase #5	$140.97	9.691%	$154.6314	$154.63	$154.65	$154.60
Purchase #6	$93.74	10.563%	$103.6418	$103.64	$103.65	$103.60
Purchase #7	$169.48	6.538%	$180.5606	$180.56	$180.55	$180.60
7 purchase totals =	$778.87		$843.4554	$843.45	$843.50	$843.40