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 $58.70   7.633%   $63.1806   $63.18   $63.20   $63.20  
  Purchase #2 $54.98   3.792%   $57.0648   $57.06   $57.05   $57.10  
  Purchase #3 $112.67   4.562%   $117.81   $117.81   $117.80   $117.80  
  Purchase #4 $225.68   10.748%   $249.9361   $249.94   $249.95   $249.90  
  Purchase #5 $247.48   6.874%   $264.4918   $264.49   $264.50   $264.50  
  Purchase #6 $111.61   6.198%   $118.5276   $118.53   $118.55   $118.50  
  Purchase #7 $241.86   4.715%   $253.2637   $253.26   $253.25   $253.30  
  7 purchase totals = $1,052.98       $1,124.2746   $1,124.27   $1,124.30   $1,124.30