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 $236.59   10.736%   $261.9903   $261.99   $262.00   $262.00  
  Purchase #2 $20.82   5.851%   $22.0382   $22.04   $22.05   $22.00  
  Purchase #3 $215.46   12.417%   $242.2137   $242.21   $242.20   $242.20  
  Purchase #4 $201.93   12.200%   $226.5655   $226.57   $226.55   $226.60  
  Purchase #5 $64.80   3.874%   $67.3104   $67.31   $67.30   $67.30  
  Purchase #6 $155.82   7.249%   $167.1154   $167.12   $167.10   $167.10  
  Purchase #7 $150.53   8.658%   $163.5629   $163.56   $163.55   $163.60  
  7 purchase totals = $1,045.95       $1,150.7964   $1,150.80   $1,150.75   $1,150.80