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	$94.44	5.765%	$99.8845	$99.88	$99.90	$99.90
Purchase #2	$17.81	9.597%	$19.5192	$19.52	$19.50	$19.50
Purchase #3	$104.66	6.151%	$111.0976	$111.10	$111.10	$111.10
Purchase #4	$30.35	4.295%	$31.6535	$31.65	$31.65	$31.70
Purchase #5	$143.36	8.259%	$155.2001	$155.20	$155.20	$155.20
Purchase #6	$196.88	12.728%	$221.9389	$221.94	$221.95	$221.90
Purchase #7	$199.84	4.236%	$208.3052	$208.31	$208.30	$208.30
7 purchase totals =	$787.34		$847.5990	$847.60	$847.60	$847.60