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 $60.26   8.845%   $65.59   $65.59   $65.60   $65.60  
  Purchase #2 $229.30   4.433%   $239.4649   $239.46   $239.45   $239.50  
  Purchase #3 $44.33   7.645%   $47.719   $47.72   $47.70   $47.70  
  Purchase #4 $182.74   13.629%   $207.6456   $207.65   $207.65   $207.60  
  Purchase #5 $228.57   8.281%   $247.4979   $247.50   $247.50   $247.50  
  Purchase #6 $249.31   11.338%   $277.5768   $277.58   $277.60   $277.60  
  Purchase #7 $213.33   9.438%   $233.4641   $233.46   $233.45   $233.50  
  7 purchase totals = $1,207.84       $1,318.9583   $1,318.96   $1,318.95   $1,319.00