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	$97.96	13.787%	$111.4657	$111.47	$111.45	$111.50
Purchase #2	$44.48	9.252%	$48.5953	$48.60	$48.60	$48.60
Purchase #3	$110.54	11.614%	$123.3781	$123.38	$123.40	$123.40
Purchase #4	$172.30	3.272%	$177.9377	$177.94	$177.95	$177.90
Purchase #5	$146.88	10.533%	$162.3509	$162.35	$162.35	$162.40
Purchase #6	$69.72	4.659%	$72.9683	$72.97	$72.95	$73.00
Purchase #7	$194.96	4.361%	$203.4622	$203.46	$203.45	$203.50
7 purchase totals =	$836.84		$900.1582	$900.17	$900.15	$900.30