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 $108.97   6.427%   $115.9735   $115.97   $115.95   $116.00  
  Purchase #2 $170.47   5.387%   $179.6532   $179.65   $179.65   $179.70  
  Purchase #3 $167.27   11.579%   $186.6382   $186.64   $186.65   $186.60  
  Purchase #4 $43.73   7.400%   $46.966   $46.97   $46.95   $47.00  
  Purchase #5 $232.31   7.816%   $250.4673   $250.47   $250.45   $250.50  
  Purchase #6 $157.80   3.257%   $162.9395   $162.94   $162.95   $162.90  
  Purchase #7 $165.54   10.446%   $182.8323   $182.83   $182.85   $182.80  
  7 purchase totals = $1,046.09       $1,125.4700   $1,125.47   $1,125.45   $1,125.50