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	$218.39	3.756%	$226.5927	$226.59	$226.60	$226.60
Purchase #2	$19.31	5.333%	$20.3398	$20.34	$20.35	$20.30
Purchase #3	$52.63	7.409%	$56.5294	$56.53	$56.55	$56.50
Purchase #4	$6.67	12.587%	$7.5096	$7.51	$7.50	$7.50
Purchase #5	$116.33	13.328%	$131.8345	$131.83	$131.85	$131.80
Purchase #6	$203.62	10.346%	$224.6865	$224.69	$224.70	$224.70
Purchase #7	$49.25	7.306%	$52.8482	$52.85	$52.85	$52.80
7 purchase totals =	$666.20		$720.3407	$720.34	$720.40	$720.20