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 $85.72   10.647%   $94.8466   $94.85   $94.85   $94.80  
  Purchase #2 $218.57   8.721%   $237.6315   $237.63   $237.65   $237.60  
  Purchase #3 $90.72   7.374%   $97.4097   $97.41   $97.40   $97.40  
  Purchase #4 $57.60   11.417%   $64.1762   $64.18   $64.20   $64.20  
  Purchase #5 $207.49   8.208%   $224.5208   $224.52   $224.50   $224.50  
  Purchase #6 $94.94   10.397%   $104.8109   $104.81   $104.80   $104.80  
  Purchase #7 $97.64   4.467%   $102.0016   $102.00   $102.00   $102.00  
  7 purchase totals = $852.68       $925.3973   $925.40   $925.40   $925.30