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	$81.55	6.568%	$86.9062	$86.91	$86.90	$86.90
Purchase #2	$77.37	9.744%	$84.9089	$84.91	$84.90	$84.90
Purchase #3	$118.31	4.443%	$123.5665	$123.57	$123.55	$123.60
Purchase #4	$169.60	13.730%	$192.8861	$192.89	$192.90	$192.90
Purchase #5	$136.46	5.610%	$144.1154	$144.12	$144.10	$144.10
Purchase #6	$128.33	13.287%	$145.3812	$145.38	$145.40	$145.40
Purchase #7	$224.79	10.683%	$248.8043	$248.80	$248.80	$248.80
7 purchase totals =	$936.41		$1,026.5686	$1,026.58	$1,026.55	$1,026.60