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	$101.39	8.440%	$109.9473	$109.95	$109.95	$109.90
Purchase #2	$126.96	5.450%	$133.8793	$133.88	$133.90	$133.90
Purchase #3	$55.77	5.686%	$58.9411	$58.94	$58.95	$58.90
Purchase #4	$67.32	10.815%	$74.6007	$74.60	$74.60	$74.60
Purchase #5	$155.86	4.507%	$162.8846	$162.88	$162.90	$162.90
Purchase #6	$123.42	11.722%	$137.8873	$137.89	$137.90	$137.90
Purchase #7	$56.70	5.382%	$59.7516	$59.75	$59.75	$59.80
7 purchase totals =	$687.42		$737.8919	$737.89	$737.95	$737.90