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	$40.33	6.462%	$42.9361	$42.94	$42.95	$42.90
Purchase #2	$13.71	7.563%	$14.7469	$14.75	$14.75	$14.70
Purchase #3	$244.31	6.215%	$259.4939	$259.49	$259.50	$259.50
Purchase #4	$203.88	13.605%	$231.6179	$231.62	$231.60	$231.60
Purchase #5	$85.43	6.309%	$90.8198	$90.82	$90.80	$90.80
Purchase #6	$144.72	12.869%	$163.344	$163.34	$163.35	$163.30
Purchase #7	$144.31	12.605%	$162.5003	$162.50	$162.50	$162.50
7 purchase totals =	$876.69		$965.4589	$965.46	$965.45	$965.30