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	$61.31	9.161%	$66.9266	$66.93	$66.95	$66.90
Purchase #2	$39.49	12.772%	$44.5337	$44.53	$44.55	$44.50
Purchase #3	$90.69	13.706%	$103.12	$103.12	$103.10	$103.10
Purchase #4	$198.59	11.746%	$221.9164	$221.92	$221.90	$221.90
Purchase #5	$208.74	11.619%	$232.9935	$232.99	$233.00	$233.00
Purchase #6	$98.44	7.178%	$105.506	$105.51	$105.50	$105.50
Purchase #7	$179.91	10.550%	$198.8905	$198.89	$198.90	$198.90
7 purchase totals =	$877.17		$973.8867	$973.89	$973.90	$973.80