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 $218.59   8.508%   $237.1876   $237.19   $237.20   $237.20  
  Purchase #2 $177.89   13.270%   $201.496   $201.50   $201.50   $201.50  
  Purchase #3 $58.94   12.737%   $66.4472   $66.45   $66.45   $66.40  
  Purchase #4 $86.58   8.788%   $94.1887   $94.19   $94.20   $94.20  
  Purchase #5 $212.48   7.757%   $228.9621   $228.96   $228.95   $229.00  
  Purchase #6 $93.28   5.414%   $98.3302   $98.33   $98.35   $98.30  
  Purchase #7 $121.40   5.434%   $127.9969   $128.00   $128.00   $128.00  
  7 purchase totals = $969.16       $1,054.6087   $1,054.62   $1,054.65   $1,054.60