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	$240.51	11.117%	$267.2475	$267.25	$267.25	$267.20
Purchase #2	$161.55	3.685%	$167.5031	$167.50	$167.50	$167.50
Purchase #3	$141.45	10.782%	$156.7011	$156.70	$156.70	$156.70
Purchase #4	$103.85	7.395%	$111.5297	$111.53	$111.55	$111.50
Purchase #5	$57.92	10.201%	$63.8284	$63.83	$63.85	$63.80
Purchase #6	$42.56	4.769%	$44.5897	$44.59	$44.60	$44.60
Purchase #7	$218.66	12.338%	$245.6383	$245.64	$245.65	$245.60
7 purchase totals =	$966.50		$1,057.0378	$1,057.04	$1,057.10	$1,056.90