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 $62.93   3.446%   $65.0986   $65.10   $65.10   $65.10  
  Purchase #2 $193.89   4.169%   $201.9733   $201.97   $201.95   $202.00  
  Purchase #3 $174.56   6.172%   $185.3338   $185.33   $185.35   $185.30  
  Purchase #4 $53.78   5.722%   $56.8573   $56.86   $56.85   $56.90  
  Purchase #5 $50.46   10.595%   $55.8062   $55.81   $55.80   $55.80  
  Purchase #6 $160.71   7.628%   $172.969   $172.97   $172.95   $173.00  
  Purchase #7 $84.25   3.297%   $87.0277   $87.03   $87.05   $87.00  
  7 purchase totals = $780.58       $825.0659   $825.07   $825.05   $825.10