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 $86.34   9.508%   $94.5492   $94.55   $94.55   $94.50  
  Purchase #2 $149.32   5.713%   $157.8507   $157.85   $157.85   $157.90  
  Purchase #3 $161.43   9.745%   $177.1614   $177.16   $177.15   $177.20  
  Purchase #4 $194.49   13.708%   $221.1507   $221.15   $221.15   $221.20  
  Purchase #5 $136.37   5.194%   $143.4531   $143.45   $143.45   $143.50  
  Purchase #6 $148.66   10.379%   $164.0894   $164.09   $164.10   $164.10  
  Purchase #7 $121.43   12.223%   $136.2724   $136.27   $136.25   $136.30  
  7 purchase totals = $998.04       $1,094.5269   $1,094.52   $1,094.50   $1,094.70