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 $184.32   9.489%   $201.8101   $201.81   $201.80   $201.80  
  Purchase #2 $179.93   6.567%   $191.746   $191.75   $191.75   $191.70  
  Purchase #3 $153.79   12.533%   $173.0645   $173.06   $173.05   $173.10  
  Purchase #4 $162.53   8.468%   $176.293   $176.29   $176.30   $176.30  
  Purchase #5 $12.93   12.155%   $14.5016   $14.50   $14.50   $14.50  
  Purchase #6 $59.26   4.458%   $61.9018   $61.90   $61.90   $61.90  
  Purchase #7 $114.40   12.675%   $128.9002   $128.90   $128.90   $128.90  
  7 purchase totals = $867.16       $948.2172   $948.21   $948.20   $948.20