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	$156.42	12.341%	$175.7238	$175.72	$175.70	$175.70
Purchase #2	$34.92	7.564%	$37.5613	$37.56	$37.55	$37.60
Purchase #3	$246.94	11.804%	$276.0888	$276.09	$276.10	$276.10
Purchase #4	$239.72	11.329%	$266.8779	$266.88	$266.90	$266.90
Purchase #5	$111.90	10.616%	$123.7793	$123.78	$123.80	$123.80
Purchase #6	$130.36	8.736%	$141.7482	$141.75	$141.75	$141.70
Purchase #7	$213.36	4.758%	$223.5117	$223.51	$223.50	$223.50
7 purchase totals =	$1,133.62		$1,245.2910	$1,245.29	$1,245.30	$1,245.30