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 $62.59   8.405%   $67.8507   $67.85   $67.85   $67.90  
  Purchase #2 $232.69   6.564%   $247.9638   $247.96   $247.95   $248.00  
  Purchase #3 $14.45   4.635%   $15.1198   $15.12   $15.10   $15.10  
  Purchase #4 $182.51   10.759%   $202.1463   $202.15   $202.15   $202.10  
  Purchase #5 $184.46   8.373%   $199.9048   $199.90   $199.90   $199.90  
  Purchase #6 $181.48   6.754%   $193.7372   $193.74   $193.75   $193.70  
  Purchase #7 $116.80   4.682%   $122.2686   $122.27   $122.25   $122.30  
  7 purchase totals = $974.98       $1,048.9912   $1,048.99   $1,048.95   $1,049.00