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	$64.59	4.528%	$67.5146	$67.51	$67.50	$67.50
Purchase #2	$47.94	10.254%	$52.8558	$52.86	$52.85	$52.90
Purchase #3	$13.70	5.610%	$14.4686	$14.47	$14.45	$14.50
Purchase #4	$93.55	12.811%	$105.5347	$105.53	$105.55	$105.50
Purchase #5	$100.64	3.467%	$104.1292	$104.13	$104.15	$104.10
Purchase #6	$167.55	8.803%	$182.2994	$182.30	$182.30	$182.30
Purchase #7	$212.38	8.870%	$231.2181	$231.22	$231.20	$231.20
7 purchase totals =	$700.35		$758.0204	$758.02	$758.00	$758.00