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 $214.56   13.528%   $243.5857   $243.59   $243.60   $243.60  
  Purchase #2 $190.74   9.755%   $209.3467   $209.35   $209.35   $209.30  
  Purchase #3 $210.83   3.296%   $217.779   $217.78   $217.80   $217.80  
  Purchase #4 $161.59   12.376%   $181.5884   $181.59   $181.60   $181.60  
  Purchase #5 $226.53   3.604%   $234.6941   $234.69   $234.70   $234.70  
  Purchase #6 $168.59   6.719%   $179.9176   $179.92   $179.90   $179.90  
  Purchase #7 $185.93   4.466%   $194.2336   $194.23   $194.25   $194.20  
  7 purchase totals = $1,358.77       $1,461.1451   $1,461.15   $1,461.20   $1,461.10