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	$205.55	13.849%	$234.0166	$234.02	$234.00	$234.00
Purchase #2	$122.54	7.826%	$132.13	$132.13	$132.15	$132.10
Purchase #3	$161.60	5.511%	$170.5058	$170.51	$170.50	$170.50
Purchase #4	$77.73	10.318%	$85.7502	$85.75	$85.75	$85.80
Purchase #5	$134.48	6.681%	$143.4646	$143.46	$143.45	$143.50
Purchase #6	$168.38	7.352%	$180.7593	$180.76	$180.75	$180.80
Purchase #7	$77.49	6.191%	$82.2874	$82.29	$82.30	$82.30
7 purchase totals =	$947.77		$1,028.9139	$1,028.92	$1,028.90	$1,029.00