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	$245.93	3.788%	$255.2458	$255.25	$255.25	$255.20
Purchase #2	$68.37	4.293%	$71.3051	$71.31	$71.30	$71.30
Purchase #3	$23.65	9.154%	$25.8149	$25.81	$25.80	$25.80
Purchase #4	$218.82	8.564%	$237.5597	$237.56	$237.55	$237.60
Purchase #5	$54.70	5.851%	$57.9005	$57.90	$57.90	$57.90
Purchase #6	$205.96	3.566%	$213.3045	$213.30	$213.30	$213.30
Purchase #7	$231.33	13.435%	$262.4092	$262.41	$262.40	$262.40
7 purchase totals =	$1,048.76		$1,123.5397	$1,123.54	$1,123.50	$1,123.50