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	$120.85	13.141%	$136.7309	$136.73	$136.75	$136.70
Purchase #2	$184.35	4.423%	$192.5038	$192.50	$192.50	$192.50
Purchase #3	$68.61	5.751%	$72.5558	$72.56	$72.55	$72.60
Purchase #4	$42.86	10.576%	$47.3929	$47.39	$47.40	$47.40
Purchase #5	$181.67	13.322%	$205.8721	$205.87	$205.85	$205.90
Purchase #6	$126.33	10.708%	$139.8574	$139.86	$139.85	$139.90
Purchase #7	$237.77	3.860%	$246.9479	$246.95	$246.95	$246.90
7 purchase totals =	$962.44		$1,041.8608	$1,041.86	$1,041.85	$1,041.90