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 $173.77   13.238%   $196.7737   $196.77   $196.75   $196.80  
  Purchase #2 $141.39   3.865%   $146.8547   $146.85   $146.85   $146.90  
  Purchase #3 $188.69   10.707%   $208.893   $208.89   $208.90   $208.90  
  Purchase #4 $88.56   10.383%   $97.7552   $97.76   $97.75   $97.80  
  Purchase #5 $171.35   11.816%   $191.5967   $191.60   $191.60   $191.60  
  Purchase #6 $112.95   10.644%   $124.9724   $124.97   $124.95   $125.00  
  Purchase #7 $213.47   7.198%   $228.8356   $228.84   $228.85   $228.80  
  7 purchase totals = $1,090.18       $1,195.6813   $1,195.68   $1,195.65   $1,195.80