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	$213.81	3.303%	$220.8721	$220.87	$220.85	$220.90
Purchase #2	$55.94	5.804%	$59.1868	$59.19	$59.20	$59.20
Purchase #3	$100.86	13.739%	$114.7172	$114.72	$114.70	$114.70
Purchase #4	$45.53	12.793%	$51.3547	$51.35	$51.35	$51.40
Purchase #5	$108.63	13.287%	$123.0637	$123.06	$123.05	$123.10
Purchase #6	$54.52	9.838%	$59.8837	$59.88	$59.90	$59.90
Purchase #7	$75.90	3.781%	$78.7698	$78.77	$78.75	$78.80
7 purchase totals =	$655.19		$707.8480	$707.84	$707.80	$708.00