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 $92.61   12.354%   $104.051   $104.05   $104.05   $104.10  
  Purchase #2 $90.97   5.191%   $95.6923   $95.69   $95.70   $95.70  
  Purchase #3 $94.49   10.837%   $104.7299   $104.73   $104.75   $104.70  
  Purchase #4 $106.64   6.861%   $113.9566   $113.96   $113.95   $114.00  
  Purchase #5 $180.49   6.326%   $191.9078   $191.91   $191.90   $191.90  
  Purchase #6 $225.90   4.189%   $235.363   $235.36   $235.35   $235.40  
  Purchase #7 $214.26   11.435%   $238.7606   $238.76   $238.75   $238.80  
  7 purchase totals = $1,005.36       $1,084.4612   $1,084.46   $1,084.45   $1,084.60