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 $58.48   5.324%   $61.5935   $61.59   $61.60   $61.60  
  Purchase #2 $58.82   8.218%   $63.6538   $63.65   $63.65   $63.70  
  Purchase #3 $56.91   3.777%   $59.0595   $59.06   $59.05   $59.10  
  Purchase #4 $88.69   6.177%   $94.1684   $94.17   $94.15   $94.20  
  Purchase #5 $13.30   6.380%   $14.1485   $14.15   $14.15   $14.10  
  Purchase #6 $227.78   3.677%   $236.1555   $236.16   $236.15   $236.20  
  Purchase #7 $212.46   13.575%   $241.3014   $241.30   $241.30   $241.30  
  7 purchase totals = $716.44       $770.0806   $770.08   $770.05   $770.20