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	$37.81	8.819%	$41.1445	$41.14	$41.15	$41.10
Purchase #2	$114.54	7.770%	$123.4398	$123.44	$123.45	$123.40
Purchase #3	$232.75	12.113%	$260.943	$260.94	$260.95	$260.90
Purchase #4	$132.47	8.189%	$143.318	$143.32	$143.30	$143.30
Purchase #5	$168.77	8.198%	$182.6058	$182.61	$182.60	$182.60
Purchase #6	$221.95	7.653%	$238.9358	$238.94	$238.95	$238.90
Purchase #7	$131.67	11.813%	$147.2242	$147.22	$147.20	$147.20
7 purchase totals =	$1,039.96		$1,137.6111	$1,137.61	$1,137.60	$1,137.40