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	$198.45	7.689%	$213.7088	$213.71	$213.70	$213.70
Purchase #2	$42.96	4.430%	$44.8631	$44.86	$44.85	$44.90
Purchase #3	$37.25	10.617%	$41.2048	$41.20	$41.20	$41.20
Purchase #4	$135.43	5.828%	$143.3229	$143.32	$143.30	$143.30
Purchase #5	$136.88	13.472%	$155.3205	$155.32	$155.30	$155.30
Purchase #6	$114.39	8.339%	$123.929	$123.93	$123.95	$123.90
Purchase #7	$180.47	5.294%	$190.0241	$190.02	$190.00	$190.00
7 purchase totals =	$845.83		$912.3732	$912.36	$912.30	$912.30