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	$201.72	3.660%	$209.103	$209.10	$209.10	$209.10
Purchase #2	$47.30	3.183%	$48.8056	$48.81	$48.80	$48.80
Purchase #3	$184.30	8.269%	$199.5398	$199.54	$199.55	$199.50
Purchase #4	$69.28	13.260%	$78.4665	$78.47	$78.45	$78.50
Purchase #5	$226.98	12.349%	$255.0098	$255.01	$255.00	$255.00
Purchase #6	$86.25	7.336%	$92.5773	$92.58	$92.60	$92.60
Purchase #7	$216.41	12.755%	$244.0131	$244.01	$244.00	$244.00
7 purchase totals =	$1,032.24		$1,127.5151	$1,127.52	$1,127.50	$1,127.50