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	$219.46	6.172%	$233.0051	$233.01	$233.00	$233.00
Purchase #2	$6.37	6.287%	$6.7705	$6.77	$6.75	$6.80
Purchase #3	$205.35	9.477%	$224.811	$224.81	$224.80	$224.80
Purchase #4	$248.81	6.445%	$264.8458	$264.85	$264.85	$264.80
Purchase #5	$23.35	10.734%	$25.8564	$25.86	$25.85	$25.90
Purchase #6	$170.99	4.583%	$178.8265	$178.83	$178.85	$178.80
Purchase #7	$231.25	13.498%	$262.4641	$262.46	$262.45	$262.50
7 purchase totals =	$1,105.58		$1,196.5794	$1,196.59	$1,196.55	$1,196.60