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	$78.54	7.789%	$84.6575	$84.66	$84.65	$84.70
Purchase #2	$80.41	13.771%	$91.4833	$91.48	$91.50	$91.50
Purchase #3	$103.46	12.626%	$116.5229	$116.52	$116.50	$116.50
Purchase #4	$58.43	13.192%	$66.1381	$66.14	$66.15	$66.10
Purchase #5	$87.28	3.618%	$90.4378	$90.44	$90.45	$90.40
Purchase #6	$197.79	5.404%	$208.4786	$208.48	$208.50	$208.50
Purchase #7	$161.85	4.627%	$169.3388	$169.34	$169.35	$169.30
7 purchase totals =	$767.76		$827.0570	$827.06	$827.10	$827.00