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 $64.26   7.385%   $69.0056   $69.01   $69.00   $69.00  
  Purchase #2 $200.98   13.541%   $228.1947   $228.19   $228.20   $228.20  
  Purchase #3 $67.87   5.639%   $71.6972   $71.70   $71.70   $71.70  
  Purchase #4 $27.64   9.266%   $30.2011   $30.20   $30.20   $30.20  
  Purchase #5 $61.50   6.248%   $65.3425   $65.34   $65.35   $65.30  
  Purchase #6 $200.65   12.186%   $225.1012   $225.10   $225.10   $225.10  
  Purchase #7 $77.34   13.346%   $87.6618   $87.66   $87.65   $87.70  
  7 purchase totals = $700.24       $777.2041   $777.20   $777.20   $777.20