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 $136.35   11.571%   $152.1271   $152.13   $152.15   $152.10  
  Purchase #2 $188.82   12.482%   $212.3885   $212.39   $212.40   $212.40  
  Purchase #3 $64.29   5.554%   $67.8607   $67.86   $67.85   $67.90  
  Purchase #4 $65.56   6.310%   $69.6968   $69.70   $69.70   $69.70  
  Purchase #5 $218.58   3.853%   $227.0019   $227.00   $227.00   $227.00  
  Purchase #6 $82.68   11.443%   $92.1411   $92.14   $92.15   $92.10  
  Purchase #7 $65.78   13.419%   $74.607   $74.61   $74.60   $74.60  
  7 purchase totals = $822.06       $895.8231   $895.83   $895.85   $895.80