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	$162.64	8.802%	$176.9556	$176.96	$176.95	$177.00
Purchase #2	$216.56	8.423%	$234.8008	$234.80	$234.80	$234.80
Purchase #3	$65.73	12.375%	$73.8641	$73.86	$73.85	$73.90
Purchase #4	$231.47	10.863%	$256.6146	$256.61	$256.60	$256.60
Purchase #5	$119.62	3.117%	$123.3486	$123.35	$123.35	$123.30
Purchase #6	$89.38	12.528%	$100.5775	$100.58	$100.60	$100.60
Purchase #7	$32.70	11.371%	$36.4183	$36.42	$36.40	$36.40
7 purchase totals =	$918.10		$1,002.5795	$1,002.58	$1,002.55	$1,002.60