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 $56.69   4.514%   $59.249   $59.25   $59.25   $59.20  
  Purchase #2 $211.85   11.767%   $236.7784   $236.78   $236.80   $236.80  
  Purchase #3 $9.75   13.566%   $11.0727   $11.07   $11.05   $11.10  
  Purchase #4 $198.37   6.840%   $211.9385   $211.94   $211.95   $211.90  
  Purchase #5 $182.29   8.362%   $197.5331   $197.53   $197.55   $197.50  
  Purchase #6 $61.29   8.467%   $66.4794   $66.48   $66.50   $66.50  
  Purchase #7 $207.72   13.283%   $235.3114   $235.31   $235.30   $235.30  
  7 purchase totals = $927.96       $1,018.3625   $1,018.36   $1,018.40   $1,018.30