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	$123.97	3.222%	$127.9643	$127.96	$127.95	$128.00
Purchase #2	$208.47	5.274%	$219.4647	$219.46	$219.45	$219.50
Purchase #3	$17.48	5.204%	$18.3897	$18.39	$18.40	$18.40
Purchase #4	$108.37	4.782%	$113.5523	$113.55	$113.55	$113.60
Purchase #5	$224.65	13.758%	$255.5573	$255.56	$255.55	$255.60
Purchase #6	$166.74	9.346%	$182.3235	$182.32	$182.30	$182.30
Purchase #7	$212.55	4.706%	$222.5526	$222.55	$222.55	$222.60
7 purchase totals =	$1,062.23		$1,139.8044	$1,139.79	$1,139.75	$1,140.00