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 $48.97   7.332%   $52.5605   $52.56   $52.55   $52.60  
  Purchase #2 $207.60   9.204%   $226.7075   $226.71   $226.70   $226.70  
  Purchase #3 $56.86   13.750%   $64.6783   $64.68   $64.70   $64.70  
  Purchase #4 $144.68   11.408%   $161.1851   $161.19   $161.20   $161.20  
  Purchase #5 $241.26   6.859%   $257.808   $257.81   $257.80   $257.80  
  Purchase #6 $230.87   10.205%   $254.4303   $254.43   $254.45   $254.40  
  Purchase #7 $217.82   5.476%   $229.7478   $229.75   $229.75   $229.70  
  7 purchase totals = $1,148.06       $1,247.1175   $1,247.13   $1,247.15   $1,247.10