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	$13.33	9.455%	$14.5904	$14.59	$14.60	$14.60
Purchase #2	$167.98	13.416%	$190.5162	$190.52	$190.50	$190.50
Purchase #3	$88.97	13.832%	$101.2763	$101.28	$101.30	$101.30
Purchase #4	$199.81	13.532%	$226.8483	$226.85	$226.85	$226.80
Purchase #5	$209.33	9.618%	$229.4634	$229.46	$229.45	$229.50
Purchase #6	$126.92	11.850%	$141.96	$141.96	$141.95	$142.00
Purchase #7	$70.94	11.107%	$78.8193	$78.82	$78.80	$78.80
7 purchase totals =	$877.28		$983.4739	$983.48	$983.45	$983.50