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 $194.59   10.281%   $214.5958   $214.60   $214.60   $214.60  
  Purchase #2 $243.52   5.677%   $257.3446   $257.34   $257.35   $257.30  
  Purchase #3 $132.95   3.360%   $137.4171   $137.42   $137.40   $137.40  
  Purchase #4 $185.85   8.244%   $201.1715   $201.17   $201.15   $201.20  
  Purchase #5 $93.98   11.697%   $104.9728   $104.97   $104.95   $105.00  
  Purchase #6 $35.49   8.744%   $38.5932   $38.59   $38.60   $38.60  
  Purchase #7 $63.50   11.176%   $70.5968   $70.60   $70.60   $70.60  
  7 purchase totals = $949.88       $1,024.6918   $1,024.69   $1,024.65   $1,024.70