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	$20.42	10.476%	$22.5592	$22.56	$22.55	$22.60
Purchase #2	$196.49	11.871%	$219.8153	$219.82	$219.80	$219.80
Purchase #3	$198.39	5.534%	$209.3689	$209.37	$209.35	$209.40
Purchase #4	$246.99	13.525%	$280.3954	$280.40	$280.40	$280.40
Purchase #5	$172.69	10.553%	$190.914	$190.91	$190.90	$190.90
Purchase #6	$134.81	9.471%	$147.5779	$147.58	$147.60	$147.60
Purchase #7	$114.32	4.821%	$119.8314	$119.83	$119.85	$119.80
7 purchase totals =	$1,084.11		$1,190.4621	$1,190.47	$1,190.45	$1,190.50