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 $160.40   13.459%   $181.9882   $181.99   $182.00   $182.00  
  Purchase #2 $63.99   5.143%   $67.281   $67.28   $67.30   $67.30  
  Purchase #3 $231.65   13.263%   $262.3737   $262.37   $262.35   $262.40  
  Purchase #4 $199.43   3.796%   $207.0004   $207.00   $207.00   $207.00  
  Purchase #5 $56.89   3.714%   $59.0029   $59.00   $59.00   $59.00  
  Purchase #6 $33.87   8.559%   $36.7689   $36.77   $36.75   $36.80  
  Purchase #7 $54.98   11.436%   $61.2675   $61.27   $61.25   $61.30  
  7 purchase totals = $801.21       $875.6826   $875.68   $875.65   $875.80