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	$119.81	3.851%	$124.4239	$124.42	$124.40	$124.40
Purchase #2	$39.80	4.438%	$41.5663	$41.57	$41.55	$41.60
Purchase #3	$173.26	6.428%	$184.3972	$184.40	$184.40	$184.40
Purchase #4	$198.57	13.473%	$225.3233	$225.32	$225.30	$225.30
Purchase #5	$215.34	10.761%	$238.5127	$238.51	$238.50	$238.50
Purchase #6	$140.34	5.174%	$147.6012	$147.60	$147.60	$147.60
Purchase #7	$102.51	11.337%	$114.1316	$114.13	$114.15	$114.10
7 purchase totals =	$989.63		$1,075.9562	$1,075.95	$1,075.90	$1,075.90