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	$35.77	5.802%	$37.8454	$37.85	$37.85	$37.80
Purchase #2	$48.53	6.838%	$51.8485	$51.85	$51.85	$51.80
Purchase #3	$23.37	3.721%	$24.2396	$24.24	$24.25	$24.20
Purchase #4	$85.47	5.767%	$90.3991	$90.40	$90.40	$90.40
Purchase #5	$216.37	8.411%	$234.5689	$234.57	$234.55	$234.60
Purchase #6	$204.51	4.346%	$213.398	$213.40	$213.40	$213.40
Purchase #7	$98.91	10.635%	$109.4291	$109.43	$109.45	$109.40
7 purchase totals =	$712.93		$761.7286	$761.74	$761.75	$761.60