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	$132.38	13.708%	$150.5267	$150.53	$150.55	$150.50
Purchase #2	$56.95	4.163%	$59.3208	$59.32	$59.30	$59.30
Purchase #3	$109.36	12.256%	$122.7632	$122.76	$122.75	$122.80
Purchase #4	$16.41	8.836%	$17.86	$17.86	$17.85	$17.90
Purchase #5	$125.34	5.274%	$131.9504	$131.95	$131.95	$132.00
Purchase #6	$131.67	6.621%	$140.3879	$140.39	$140.40	$140.40
Purchase #7	$91.49	10.526%	$101.1202	$101.12	$101.10	$101.10
7 purchase totals =	$663.60		$723.9292	$723.93	$723.90	$724.00