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	$101.91	9.554%	$111.6465	$111.65	$111.65	$111.60
Purchase #2	$181.47	13.328%	$205.6563	$205.66	$205.65	$205.70
Purchase #3	$121.63	5.503%	$128.3233	$128.32	$128.30	$128.30
Purchase #4	$134.51	13.641%	$152.8585	$152.86	$152.85	$152.90
Purchase #5	$41.47	4.681%	$43.4112	$43.41	$43.40	$43.40
Purchase #6	$237.60	13.814%	$270.4221	$270.42	$270.40	$270.40
Purchase #7	$97.91	12.150%	$109.8061	$109.81	$109.80	$109.80
7 purchase totals =	$916.50		$1,022.1240	$1,022.13	$1,022.05	$1,022.10