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	$213.71	6.346%	$227.272	$227.27	$227.25	$227.30
Purchase #2	$131.41	8.326%	$142.3512	$142.35	$142.35	$142.40
Purchase #3	$196.80	9.501%	$215.498	$215.50	$215.50	$215.50
Purchase #4	$189.44	12.869%	$213.819	$213.82	$213.80	$213.80
Purchase #5	$63.47	7.702%	$68.3585	$68.36	$68.35	$68.40
Purchase #6	$40.40	13.161%	$45.717	$45.72	$45.70	$45.70
Purchase #7	$55.73	12.189%	$62.5229	$62.52	$62.50	$62.50
7 purchase totals =	$890.96		$975.5386	$975.54	$975.45	$975.60