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	$87.79	3.588%	$90.9399	$90.94	$90.95	$90.90
Purchase #2	$190.45	7.683%	$205.0823	$205.08	$205.10	$205.10
Purchase #3	$205.95	9.480%	$225.4741	$225.47	$225.45	$225.50
Purchase #4	$114.40	3.588%	$118.5047	$118.50	$118.50	$118.50
Purchase #5	$154.41	11.829%	$172.6752	$172.68	$172.70	$172.70
Purchase #6	$102.43	10.162%	$112.8389	$112.84	$112.85	$112.80
Purchase #7	$224.46	6.264%	$238.5202	$238.52	$238.50	$238.50
7 purchase totals =	$1,079.89		$1,164.0353	$1,164.03	$1,164.05	$1,164.00