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	$140.45	11.260%	$156.2647	$156.26	$156.25	$156.30
Purchase #2	$239.78	12.119%	$268.8389	$268.84	$268.85	$268.80
Purchase #3	$7.60	10.314%	$8.3839	$8.38	$8.40	$8.40
Purchase #4	$206.48	4.442%	$215.6518	$215.65	$215.65	$215.70
Purchase #5	$85.90	7.620%	$92.4456	$92.45	$92.45	$92.40
Purchase #6	$111.51	4.260%	$116.2603	$116.26	$116.25	$116.30
Purchase #7	$143.40	10.835%	$158.9374	$158.94	$158.95	$158.90
7 purchase totals =	$935.12		$1,016.7826	$1,016.78	$1,016.80	$1,016.80