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	$38.30	11.380%	$42.6585	$42.66	$42.65	$42.70
Purchase #2	$176.25	12.525%	$198.3253	$198.33	$198.35	$198.30
Purchase #3	$246.69	13.871%	$280.9084	$280.91	$280.90	$280.90
Purchase #4	$238.80	7.207%	$256.0103	$256.01	$256.00	$256.00
Purchase #5	$188.38	12.820%	$212.5303	$212.53	$212.55	$212.50
Purchase #6	$137.32	7.584%	$147.7343	$147.73	$147.75	$147.70
Purchase #7	$63.43	5.358%	$66.8286	$66.83	$66.85	$66.80
7 purchase totals =	$1,089.17		$1,204.9957	$1,205.00	$1,205.05	$1,204.90