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 $91.55   4.722%   $95.873   $95.87   $95.85   $95.90  
  Purchase #2 $138.33   11.741%   $154.5713   $154.57   $154.55   $154.60  
  Purchase #3 $231.61   13.520%   $262.9237   $262.92   $262.90   $262.90  
  Purchase #4 $162.37   10.289%   $179.0762   $179.08   $179.10   $179.10  
  Purchase #5 $235.83   7.575%   $253.6941   $253.69   $253.70   $253.70  
  Purchase #6 $57.59   13.629%   $65.4389   $65.44   $65.45   $65.40  
  Purchase #7 $244.74   7.805%   $263.842   $263.84   $263.85   $263.80  
  7 purchase totals = $1,162.02       $1,275.4192   $1,275.41   $1,275.40   $1,275.40