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 $62.59   7.321%   $67.1722   $67.17   $67.15   $67.20  
  Purchase #2 $183.31   13.119%   $207.3584   $207.36   $207.35   $207.40  
  Purchase #3 $74.55   8.634%   $80.9866   $80.99   $81.00   $81.00  
  Purchase #4 $210.64   11.262%   $234.3623   $234.36   $234.35   $234.40  
  Purchase #5 $189.87   11.426%   $211.5645   $211.56   $211.55   $211.60  
  Purchase #6 $167.38   8.846%   $182.1864   $182.19   $182.20   $182.20  
  Purchase #7 $170.29   4.481%   $177.9207   $177.92   $177.90   $177.90  
  7 purchase totals = $1,058.63       $1,161.5511   $1,161.55   $1,161.50   $1,161.70