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 $191.85   8.417%   $207.998   $208.00   $208.00   $208.00  
  Purchase #2 $55.90   9.263%   $61.078   $61.08   $61.10   $61.10  
  Purchase #3 $68.66   11.430%   $76.5078   $76.51   $76.50   $76.50  
  Purchase #4 $65.86   8.417%   $71.4034   $71.40   $71.40   $71.40  
  Purchase #5 $188.84   11.403%   $210.3734   $210.37   $210.35   $210.40  
  Purchase #6 $244.26   5.250%   $257.0837   $257.08   $257.10   $257.10  
  Purchase #7 $164.47   6.588%   $175.3053   $175.31   $175.30   $175.30  
  7 purchase totals = $979.84       $1,059.7496   $1,059.75   $1,059.75   $1,059.80