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	$117.38	12.665%	$132.2462	$132.25	$132.25	$132.20
Purchase #2	$56.75	6.314%	$60.3332	$60.33	$60.35	$60.30
Purchase #3	$93.48	7.289%	$100.2938	$100.29	$100.30	$100.30
Purchase #4	$130.95	13.736%	$148.9373	$148.94	$148.95	$148.90
Purchase #5	$41.29	5.262%	$43.4627	$43.46	$43.45	$43.50
Purchase #6	$113.92	5.236%	$119.8849	$119.88	$119.90	$119.90
Purchase #7	$162.82	7.692%	$175.3441	$175.34	$175.35	$175.30
7 purchase totals =	$716.59		$780.5022	$780.49	$780.55	$780.40