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 $174.59   11.151%   $194.0585   $194.06   $194.05   $194.10  
  Purchase #2 $196.87   13.741%   $223.9219   $223.92   $223.90   $223.90  
  Purchase #3 $182.57   9.541%   $199.989   $199.99   $200.00   $200.00  
  Purchase #4 $223.32   5.181%   $234.8902   $234.89   $234.90   $234.90  
  Purchase #5 $170.63   4.420%   $178.1718   $178.17   $178.15   $178.20  
  Purchase #6 $185.96   10.570%   $205.616   $205.62   $205.60   $205.60  
  Purchase #7 $59.91   8.562%   $65.0395   $65.04   $65.05   $65.00  
  7 purchase totals = $1,193.85       $1,301.6869   $1,301.69   $1,301.65   $1,301.70