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 $214.78   5.548%   $226.696   $226.70   $226.70   $226.70  
  Purchase #2 $77.36   13.838%   $88.0651   $88.07   $88.05   $88.10  
  Purchase #3 $128.28   11.837%   $143.4645   $143.46   $143.45   $143.50  
  Purchase #4 $97.79   6.788%   $104.428   $104.43   $104.45   $104.40  
  Purchase #5 $164.96   3.267%   $170.3492   $170.35   $170.35   $170.30  
  Purchase #6 $6.31   3.222%   $6.5133   $6.51   $6.50   $6.50  
  Purchase #7 $248.29   10.765%   $275.0184   $275.02   $275.00   $275.00  
  7 purchase totals = $937.77       $1,014.5345   $1,014.54   $1,014.50   $1,014.50