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	$104.31	10.818%	$115.5943	$115.59	$115.60	$115.60
Purchase #2	$172.79	7.247%	$185.3121	$185.31	$185.30	$185.30
Purchase #3	$29.78	4.220%	$31.0367	$31.04	$31.05	$31.00
Purchase #4	$31.81	3.560%	$32.9424	$32.94	$32.95	$32.90
Purchase #5	$218.81	8.300%	$236.9712	$236.97	$236.95	$237.00
Purchase #6	$240.59	6.359%	$255.8891	$255.89	$255.90	$255.90
Purchase #7	$234.48	8.693%	$254.8633	$254.86	$254.85	$254.90
7 purchase totals =	$1,032.57		$1,112.6091	$1,112.60	$1,112.60	$1,112.60