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	$126.86	11.751%	$141.7673	$141.77	$141.75	$141.80
Purchase #2	$148.99	12.863%	$168.1546	$168.15	$168.15	$168.20
Purchase #3	$213.42	8.302%	$231.1381	$231.14	$231.15	$231.10
Purchase #4	$59.31	12.578%	$66.77	$66.77	$66.75	$66.80
Purchase #5	$168.88	10.662%	$186.886	$186.89	$186.90	$186.90
Purchase #6	$216.37	4.785%	$226.7233	$226.72	$226.70	$226.70
Purchase #7	$44.80	3.663%	$46.441	$46.44	$46.45	$46.40
7 purchase totals =	$978.63		$1,067.8803	$1,067.88	$1,067.85	$1,067.90