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 $58.77   4.708%   $61.5369   $61.54   $61.55   $61.50  
  Purchase #2 $118.57   5.425%   $125.0024   $125.00   $125.00   $125.00  
  Purchase #3 $112.31   5.383%   $118.3556   $118.36   $118.35   $118.40  
  Purchase #4 $133.74   3.808%   $138.8328   $138.83   $138.85   $138.80  
  Purchase #5 $101.56   8.187%   $109.8747   $109.87   $109.85   $109.90  
  Purchase #6 $189.55   6.203%   $201.3078   $201.31   $201.30   $201.30  
  Purchase #7 $249.26   11.459%   $277.8227   $277.82   $277.80   $277.80  
  7 purchase totals = $963.76       $1,032.7329   $1,032.73   $1,032.70   $1,032.70