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 $213.81   10.706%   $236.7005   $236.70   $236.70   $236.70  
  Purchase #2 $179.67   10.572%   $198.6647   $198.66   $198.65   $198.70  
  Purchase #3 $118.70   5.283%   $124.9709   $124.97   $124.95   $125.00  
  Purchase #4 $37.82   10.518%   $41.7979   $41.80   $41.80   $41.80  
  Purchase #5 $22.45   12.820%   $25.3281   $25.33   $25.35   $25.30  
  Purchase #6 $197.31   5.418%   $208.0003   $208.00   $208.00   $208.00  
  Purchase #7 $250.77   10.253%   $276.4814   $276.48   $276.50   $276.50  
  7 purchase totals = $1,020.53       $1,111.9438   $1,111.94   $1,111.95   $1,112.00