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	$192.83	13.405%	$218.6789	$218.68	$218.70	$218.70
Purchase #2	$225.30	13.839%	$256.4793	$256.48	$256.50	$256.50
Purchase #3	$90.77	6.341%	$96.5257	$96.53	$96.55	$96.50
Purchase #4	$169.69	12.597%	$191.0658	$191.07	$191.05	$191.10
Purchase #5	$227.28	10.794%	$251.8126	$251.81	$251.80	$251.80
Purchase #6	$192.94	12.410%	$216.8839	$216.88	$216.90	$216.90
Purchase #7	$226.33	5.380%	$238.5066	$238.51	$238.50	$238.50
7 purchase totals =	$1,325.14		$1,469.9528	$1,469.96	$1,470.00	$1,470.00