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	$185.60	12.525%	$208.8464	$208.85	$208.85	$208.80
Purchase #2	$103.93	10.505%	$114.8478	$114.85	$114.85	$114.80
Purchase #3	$141.94	11.317%	$158.0033	$158.00	$158.00	$158.00
Purchase #4	$162.57	7.465%	$174.7059	$174.71	$174.70	$174.70
Purchase #5	$184.83	8.698%	$200.9065	$200.91	$200.90	$200.90
Purchase #6	$88.25	9.375%	$96.5234	$96.52	$96.50	$96.50
Purchase #7	$65.42	11.599%	$73.0081	$73.01	$73.00	$73.00
7 purchase totals =	$932.54		$1,026.8414	$1,026.85	$1,026.80	$1,026.70