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	$190.44	8.303%	$206.2522	$206.25	$206.25	$206.30
Purchase #2	$21.91	9.272%	$23.9415	$23.94	$23.95	$23.90
Purchase #3	$213.80	4.312%	$223.0191	$223.02	$223.00	$223.00
Purchase #4	$103.64	5.525%	$109.3661	$109.37	$109.35	$109.40
Purchase #5	$51.41	4.475%	$53.7106	$53.71	$53.70	$53.70
Purchase #6	$153.78	9.836%	$168.9058	$168.91	$168.90	$168.90
Purchase #7	$80.76	12.446%	$90.8114	$90.81	$90.80	$90.80
7 purchase totals =	$815.74		$876.0067	$876.01	$875.95	$876.00