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	$228.71	11.737%	$255.5537	$255.55	$255.55	$255.60
Purchase #2	$108.42	3.797%	$112.5367	$112.54	$112.55	$112.50
Purchase #3	$69.46	13.260%	$78.6704	$78.67	$78.65	$78.70
Purchase #4	$215.30	7.330%	$231.0815	$231.08	$231.10	$231.10
Purchase #5	$74.68	7.682%	$80.4169	$80.42	$80.40	$80.40
Purchase #6	$250.68	4.221%	$261.2612	$261.26	$261.25	$261.30
Purchase #7	$199.28	4.571%	$208.3891	$208.39	$208.40	$208.40
7 purchase totals =	$1,146.53		$1,227.9095	$1,227.91	$1,227.90	$1,228.00