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 $87.74   8.128%   $94.8715   $94.87   $94.85   $94.90  
  Purchase #2 $76.58   3.420%   $79.199   $79.20   $79.20   $79.20  
  Purchase #3 $73.48   6.408%   $78.1886   $78.19   $78.20   $78.20  
  Purchase #4 $241.63   8.872%   $263.0674   $263.07   $263.05   $263.10  
  Purchase #5 $203.46   11.426%   $226.7073   $226.71   $226.70   $226.70  
  Purchase #6 $109.61   8.560%   $118.9926   $118.99   $119.00   $119.00  
  Purchase #7 $209.25   11.798%   $233.9373   $233.94   $233.95   $233.90  
  7 purchase totals = $1,001.75       $1,094.9637   $1,094.97   $1,094.95   $1,095.00