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	$182.63	5.614%	$192.8828	$192.88	$192.90	$192.90
Purchase #2	$179.50	8.314%	$194.4236	$194.42	$194.40	$194.40
Purchase #3	$116.98	7.864%	$126.1793	$126.18	$126.20	$126.20
Purchase #4	$58.84	12.831%	$66.3898	$66.39	$66.40	$66.40
Purchase #5	$40.40	4.254%	$42.1186	$42.12	$42.10	$42.10
Purchase #6	$229.70	11.398%	$255.8812	$255.88	$255.90	$255.90
Purchase #7	$191.95	9.439%	$210.0682	$210.07	$210.05	$210.10
7 purchase totals =	$1,000.00		$1,087.9435	$1,087.94	$1,087.95	$1,088.00