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 $243.97   7.696%   $262.7459   $262.75   $262.75   $262.70  
  Purchase #2 $163.94   12.456%   $184.3604   $184.36   $184.35   $184.40  
  Purchase #3 $71.60   9.450%   $78.3662   $78.37   $78.35   $78.40  
  Purchase #4 $63.61   13.523%   $72.212   $72.21   $72.20   $72.20  
  Purchase #5 $177.26   11.484%   $197.6165   $197.62   $197.60   $197.60  
  Purchase #6 $181.67   3.150%   $187.3926   $187.39   $187.40   $187.40  
  Purchase #7 $155.57   10.503%   $171.9095   $171.91   $171.90   $171.90  
  7 purchase totals = $1,057.62       $1,154.6031   $1,154.61   $1,154.55   $1,154.60