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 $87.69   8.254%   $94.9279   $94.93   $94.95   $94.90  
  Purchase #2 $192.92   4.785%   $202.1512   $202.15   $202.15   $202.20  
  Purchase #3 $217.69   7.480%   $233.9732   $233.97   $233.95   $234.00  
  Purchase #4 $72.91   12.605%   $82.1003   $82.10   $82.10   $82.10  
  Purchase #5 $60.57   9.206%   $66.1461   $66.15   $66.15   $66.10  
  Purchase #6 $210.75   5.765%   $222.8997   $222.90   $222.90   $222.90  
  Purchase #7 $100.91   9.618%   $110.6155   $110.62   $110.60   $110.60  
  7 purchase totals = $943.44       $1,012.8139   $1,012.82   $1,012.80   $1,012.80