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 $162.59   13.736%   $184.9234   $184.92   $184.90   $184.90  
  Purchase #2 $233.93   3.139%   $241.2731   $241.27   $241.25   $241.30  
  Purchase #3 $142.60   3.770%   $147.976   $147.98   $148.00   $148.00  
  Purchase #4 $132.69   11.248%   $147.615   $147.62   $147.60   $147.60  
  Purchase #5 $31.33   12.193%   $35.1501   $35.15   $35.15   $35.20  
  Purchase #6 $130.98   3.839%   $136.0083   $136.01   $136.00   $136.00  
  Purchase #7 $92.70   10.689%   $102.6087   $102.61   $102.60   $102.60  
  7 purchase totals = $926.82       $995.5546   $995.56   $995.50   $995.60