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 $57.38   7.588%   $61.734   $61.73   $61.75   $61.70  
  Purchase #2 $250.93   4.223%   $261.5268   $261.53   $261.55   $261.50  
  Purchase #3 $235.52   6.661%   $251.208   $251.21   $251.20   $251.20  
  Purchase #4 $84.57   4.495%   $88.3714   $88.37   $88.35   $88.40  
  Purchase #5 $10.38   9.695%   $11.3863   $11.39   $11.40   $11.40  
  Purchase #6 $203.64   7.122%   $218.1432   $218.14   $218.15   $218.10  
  Purchase #7 $153.27   3.118%   $158.049   $158.05   $158.05   $158.00  
  7 purchase totals = $995.69       $1,050.4187   $1,050.42   $1,050.45   $1,050.30