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 $219.36   3.463%   $226.9564   $226.96   $226.95   $227.00  
  Purchase #2 $59.34   4.537%   $62.0323   $62.03   $62.05   $62.00  
  Purchase #3 $8.38   13.524%   $9.5133   $9.51   $9.50   $9.50  
  Purchase #4 $26.87   5.724%   $28.408   $28.41   $28.40   $28.40  
  Purchase #5 $54.90   7.239%   $58.8742   $58.87   $58.85   $58.90  
  Purchase #6 $42.44   9.251%   $46.3661   $46.37   $46.35   $46.40  
  Purchase #7 $23.79   8.830%   $25.8907   $25.89   $25.90   $25.90  
  7 purchase totals = $435.08       $458.0410   $458.04   $458.00   $458.10