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	$216.33	10.381%	$238.7872	$238.79	$238.80	$238.80
Purchase #2	$185.94	12.303%	$208.8162	$208.82	$208.80	$208.80
Purchase #3	$248.88	13.654%	$282.8621	$282.86	$282.85	$282.90
Purchase #4	$210.78	7.245%	$226.051	$226.05	$226.05	$226.10
Purchase #5	$60.99	10.357%	$67.3067	$67.31	$67.30	$67.30
Purchase #6	$98.32	13.389%	$111.4841	$111.48	$111.50	$111.50
Purchase #7	$95.85	13.772%	$109.0505	$109.05	$109.05	$109.10
7 purchase totals =	$1,117.09		$1,244.3578	$1,244.36	$1,244.35	$1,244.50