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	$210.67	11.678%	$235.272	$235.27	$235.25	$235.30
Purchase #2	$208.49	10.223%	$229.8039	$229.80	$229.80	$229.80
Purchase #3	$142.48	5.863%	$150.8336	$150.83	$150.85	$150.80
Purchase #4	$50.95	12.453%	$57.2948	$57.29	$57.30	$57.30
Purchase #5	$112.49	9.571%	$123.2564	$123.26	$123.25	$123.30
Purchase #6	$220.93	4.724%	$231.3667	$231.37	$231.35	$231.40
Purchase #7	$36.56	5.135%	$38.4374	$38.44	$38.45	$38.40
7 purchase totals =	$982.57		$1,066.2648	$1,066.26	$1,066.25	$1,066.30