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	$119.91	13.852%	$136.5199	$136.52	$136.50	$136.50
Purchase #2	$90.55	4.676%	$94.7841	$94.78	$94.80	$94.80
Purchase #3	$225.77	4.702%	$236.3857	$236.39	$236.40	$236.40
Purchase #4	$11.78	13.620%	$13.3844	$13.38	$13.40	$13.40
Purchase #5	$200.78	5.333%	$211.4876	$211.49	$211.50	$211.50
Purchase #6	$139.45	7.177%	$149.4583	$149.46	$149.45	$149.50
Purchase #7	$203.56	6.533%	$216.8586	$216.86	$216.85	$216.90
7 purchase totals =	$991.80		$1,058.8786	$1,058.88	$1,058.90	$1,059.00