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	$22.54	13.411%	$25.5628	$25.56	$25.55	$25.60
Purchase #2	$42.36	8.571%	$45.9907	$45.99	$46.00	$46.00
Purchase #3	$29.52	10.718%	$32.684	$32.68	$32.70	$32.70
Purchase #4	$192.54	12.149%	$215.9317	$215.93	$215.95	$215.90
Purchase #5	$59.94	4.856%	$62.8507	$62.85	$62.85	$62.90
Purchase #6	$101.41	9.782%	$111.3299	$111.33	$111.35	$111.30
Purchase #7	$177.90	7.448%	$191.15	$191.15	$191.15	$191.20
7 purchase totals =	$626.21		$685.4998	$685.49	$685.55	$685.60