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	$230.44	10.569%	$254.7952	$254.80	$254.80	$254.80
Purchase #2	$29.58	11.615%	$33.0157	$33.02	$33.00	$33.00
Purchase #3	$111.98	12.343%	$125.8017	$125.80	$125.80	$125.80
Purchase #4	$167.35	7.377%	$179.6954	$179.70	$179.70	$179.70
Purchase #5	$47.60	8.626%	$51.706	$51.71	$51.70	$51.70
Purchase #6	$88.40	13.568%	$100.3941	$100.39	$100.40	$100.40
Purchase #7	$80.97	10.661%	$89.6022	$89.60	$89.60	$89.60
7 purchase totals =	$756.32		$835.0103	$835.02	$835.00	$835.00