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	$193.94	11.618%	$216.4719	$216.47	$216.45	$216.50
Purchase #2	$169.38	6.168%	$179.8274	$179.83	$179.85	$179.80
Purchase #3	$134.30	8.188%	$145.2965	$145.30	$145.30	$145.30
Purchase #4	$211.55	12.484%	$237.9599	$237.96	$237.95	$238.00
Purchase #5	$18.32	9.641%	$20.0862	$20.09	$20.10	$20.10
Purchase #6	$103.54	8.637%	$112.4827	$112.48	$112.50	$112.50
Purchase #7	$136.56	13.439%	$154.9123	$154.91	$154.90	$154.90
7 purchase totals =	$967.59		$1,067.0369	$1,067.04	$1,067.05	$1,067.10