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 $179.74   9.790%   $197.3365   $197.34   $197.35   $197.30  
  Purchase #2 $168.78   4.474%   $176.3312   $176.33   $176.35   $176.30  
  Purchase #3 $240.83   10.694%   $266.5844   $266.58   $266.60   $266.60  
  Purchase #4 $69.87   11.241%   $77.7241   $77.72   $77.70   $77.70  
  Purchase #5 $190.33   13.227%   $215.5049   $215.50   $215.50   $215.50  
  Purchase #6 $216.72   6.689%   $231.2164   $231.22   $231.20   $231.20  
  Purchase #7 $49.65   10.721%   $54.973   $54.97   $54.95   $55.00  
  7 purchase totals = $1,115.92       $1,219.6705   $1,219.66   $1,219.65   $1,219.60