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 $88.87   7.484%   $95.521   $95.52   $95.50   $95.50  
  Purchase #2 $242.49   6.223%   $257.5802   $257.58   $257.60   $257.60  
  Purchase #3 $182.37   12.121%   $204.4751   $204.48   $204.50   $204.50  
  Purchase #4 $239.43   12.815%   $270.113   $270.11   $270.10   $270.10  
  Purchase #5 $144.96   13.199%   $164.0933   $164.09   $164.10   $164.10  
  Purchase #6 $184.61   12.439%   $207.5736   $207.57   $207.55   $207.60  
  Purchase #7 $193.76   7.566%   $208.4199   $208.42   $208.40   $208.40  
  7 purchase totals = $1,276.49       $1,407.7761   $1,407.77   $1,407.75   $1,407.80