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 $14.41   3.747%   $14.9499   $14.95   $14.95   $14.90  
  Purchase #2 $78.41   8.853%   $85.3516   $85.35   $85.35   $85.40  
  Purchase #3 $120.36   10.189%   $132.6235   $132.62   $132.60   $132.60  
  Purchase #4 $91.67   11.331%   $102.0571   $102.06   $102.05   $102.10  
  Purchase #5 $94.52   7.262%   $101.384   $101.38   $101.40   $101.40  
  Purchase #6 $21.78   11.724%   $24.3335   $24.33   $24.35   $24.30  
  Purchase #7 $12.80   12.517%   $14.4022   $14.40   $14.40   $14.40  
  7 purchase totals = $433.95       $475.1018   $475.09   $475.10   $475.10