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 $119.50   12.415%   $134.3359   $134.34   $134.35   $134.30  
  Purchase #2 $171.77   4.414%   $179.3519   $179.35   $179.35   $179.40  
  Purchase #3 $244.52   7.295%   $262.3577   $262.36   $262.35   $262.40  
  Purchase #4 $168.97   13.859%   $192.3876   $192.39   $192.40   $192.40  
  Purchase #5 $189.75   13.126%   $214.6566   $214.66   $214.65   $214.70  
  Purchase #6 $98.62   4.330%   $102.8902   $102.89   $102.90   $102.90  
  Purchase #7 $26.33   3.684%   $27.3   $27.30   $27.30   $27.30  
  7 purchase totals = $1,019.46       $1,113.2799   $1,113.29   $1,113.30   $1,113.40