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 $38.43   13.760%   $43.718   $43.72   $43.70   $43.70  
  Purchase #2 $167.91   8.581%   $182.3184   $182.32   $182.30   $182.30  
  Purchase #3 $116.87   8.261%   $126.5246   $126.52   $126.50   $126.50  
  Purchase #4 $250.75   10.813%   $277.8636   $277.86   $277.85   $277.90  
  Purchase #5 $161.43   10.758%   $178.7966   $178.80   $178.80   $178.80  
  Purchase #6 $146.38   5.316%   $154.1616   $154.16   $154.15   $154.20  
  Purchase #7 $55.68   11.340%   $61.9941   $61.99   $62.00   $62.00  
  7 purchase totals = $937.45       $1,025.3769   $1,025.37   $1,025.30   $1,025.40