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	$213.73	9.192%	$233.3761	$233.38	$233.40	$233.40
Purchase #2	$20.65	10.814%	$22.8831	$22.88	$22.90	$22.90
Purchase #3	$43.45	12.328%	$48.8065	$48.81	$48.80	$48.80
Purchase #4	$129.68	10.367%	$143.1239	$143.12	$143.10	$143.10
Purchase #5	$36.88	8.213%	$39.909	$39.91	$39.90	$39.90
Purchase #6	$39.61	12.166%	$44.429	$44.43	$44.45	$44.40
Purchase #7	$51.57	3.693%	$53.4745	$53.47	$53.45	$53.50
7 purchase totals =	$535.57		$586.0021	$586.00	$586.00	$586.00