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 $211.63   10.426%   $233.6945   $233.69   $233.70   $233.70  
  Purchase #2 $248.55   11.567%   $277.2998   $277.30   $277.30   $277.30  
  Purchase #3 $32.97   6.168%   $35.0036   $35.00   $35.00   $35.00  
  Purchase #4 $108.33   13.716%   $123.1885   $123.19   $123.20   $123.20  
  Purchase #5 $170.36   5.282%   $179.3584   $179.36   $179.35   $179.40  
  Purchase #6 $232.95   10.595%   $257.6311   $257.63   $257.65   $257.60  
  Purchase #7 $59.49   13.763%   $67.6776   $67.68   $67.70   $67.70  
  7 purchase totals = $1,064.28       $1,173.8535   $1,173.85   $1,173.90   $1,173.90