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	$132.32	6.860%	$141.3972	$141.40	$141.40	$141.40
Purchase #2	$27.45	13.457%	$31.1439	$31.14	$31.15	$31.10
Purchase #3	$225.57	12.342%	$253.4098	$253.41	$253.40	$253.40
Purchase #4	$175.74	5.219%	$184.9119	$184.91	$184.90	$184.90
Purchase #5	$179.25	11.167%	$199.2668	$199.27	$199.25	$199.30
Purchase #6	$158.63	12.182%	$177.9543	$177.95	$177.95	$178.00
Purchase #7	$85.52	5.742%	$90.4306	$90.43	$90.45	$90.40
7 purchase totals =	$984.48		$1,078.5145	$1,078.51	$1,078.50	$1,078.50