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	$141.54	6.526%	$150.7769	$150.78	$150.80	$150.80
Purchase #2	$90.57	10.797%	$100.3488	$100.35	$100.35	$100.30
Purchase #3	$53.95	7.309%	$57.8932	$57.89	$57.90	$57.90
Purchase #4	$245.38	10.682%	$271.5915	$271.59	$271.60	$271.60
Purchase #5	$182.37	8.714%	$198.2617	$198.26	$198.25	$198.30
Purchase #6	$178.37	12.696%	$201.0159	$201.02	$201.00	$201.00
Purchase #7	$118.64	4.516%	$123.9978	$124.00	$124.00	$124.00
7 purchase totals =	$1,010.82		$1,103.8858	$1,103.89	$1,103.90	$1,103.90