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 $114.52   10.430%   $126.4644   $126.46   $126.45   $126.50  
  Purchase #2 $223.89   8.462%   $242.8356   $242.84   $242.85   $242.80  
  Purchase #3 $189.63   4.269%   $197.7253   $197.73   $197.75   $197.70  
  Purchase #4 $5.28   12.872%   $5.9596   $5.96   $5.95   $6.00  
  Purchase #5 $30.45   10.684%   $33.7033   $33.70   $33.70   $33.70  
  Purchase #6 $225.67   3.523%   $233.6204   $233.62   $233.60   $233.60  
  Purchase #7 $242.69   11.776%   $271.2692   $271.27   $271.25   $271.30  
  7 purchase totals = $1,032.13       $1,111.5778   $1,111.58   $1,111.55   $1,111.60