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 $22.84   13.676%   $25.9636   $25.96   $25.95   $26.00  
  Purchase #2 $235.61   10.354%   $260.0051   $260.01   $260.00   $260.00  
  Purchase #3 $51.56   12.364%   $57.9349   $57.93   $57.95   $57.90  
  Purchase #4 $185.39   5.198%   $195.0266   $195.03   $195.05   $195.00  
  Purchase #5 $50.81   5.663%   $53.6874   $53.69   $53.70   $53.70  
  Purchase #6 $215.89   6.223%   $229.3248   $229.32   $229.30   $229.30  
  Purchase #7 $243.50   5.698%   $257.3746   $257.37   $257.35   $257.40  
  7 purchase totals = $1,005.60       $1,079.3170   $1,079.31   $1,079.30   $1,079.30