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	$66.46	8.711%	$72.2493	$72.25	$72.25	$72.20
Purchase #2	$138.57	7.339%	$148.7397	$148.74	$148.75	$148.70
Purchase #3	$117.64	11.505%	$131.1745	$131.17	$131.15	$131.20
Purchase #4	$158.67	11.191%	$176.4268	$176.43	$176.45	$176.40
Purchase #5	$182.89	7.545%	$196.6891	$196.69	$196.70	$196.70
Purchase #6	$48.54	4.854%	$50.8961	$50.90	$50.90	$50.90
Purchase #7	$13.32	10.558%	$14.7263	$14.73	$14.75	$14.70
7 purchase totals =	$726.09		$790.9018	$790.91	$790.95	$790.80