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 $199.57   9.355%   $218.2398   $218.24   $218.25   $218.20  
  Purchase #2 $177.45   13.315%   $201.0775   $201.08   $201.10   $201.10  
  Purchase #3 $56.43   13.503%   $64.0497   $64.05   $64.05   $64.00  
  Purchase #4 $54.27   10.559%   $60.0004   $60.00   $60.00   $60.00  
  Purchase #5 $104.81   3.689%   $108.6764   $108.68   $108.70   $108.70  
  Purchase #6 $159.29   3.278%   $164.5115   $164.51   $164.50   $164.50  
  Purchase #7 $203.37   13.554%   $230.9348   $230.93   $230.95   $230.90  
  7 purchase totals = $955.19       $1,047.4901   $1,047.49   $1,047.55   $1,047.40