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 $235.29   5.263%   $247.6733   $247.67   $247.65   $247.70  
  Purchase #2 $25.34   8.411%   $27.4713   $27.47   $27.45   $27.50  
  Purchase #3 $175.85   12.207%   $197.316   $197.32   $197.30   $197.30  
  Purchase #4 $52.62   7.697%   $56.6702   $56.67   $56.65   $56.70  
  Purchase #5 $157.65   12.439%   $177.2601   $177.26   $177.25   $177.30  
  Purchase #6 $163.87   9.284%   $179.0837   $179.08   $179.10   $179.10  
  Purchase #7 $157.80   11.202%   $175.4768   $175.48   $175.50   $175.50  
  7 purchase totals = $968.42       $1,060.9514   $1,060.95   $1,060.90   $1,061.10