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 $61.25   13.536%   $69.5408   $69.54   $69.55   $69.50  
  Purchase #2 $190.72   6.743%   $203.5802   $203.58   $203.60   $203.60  
  Purchase #3 $134.26   10.664%   $148.5775   $148.58   $148.60   $148.60  
  Purchase #4 $181.70   9.501%   $198.9633   $198.96   $198.95   $199.00  
  Purchase #5 $215.38   10.858%   $238.766   $238.77   $238.75   $238.80  
  Purchase #6 $215.46   12.298%   $241.9573   $241.96   $241.95   $242.00  
  Purchase #7 $197.31   3.696%   $204.6026   $204.60   $204.60   $204.60  
  7 purchase totals = $1,196.08       $1,305.9877   $1,305.99   $1,306.00   $1,306.10