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 $61.95   10.490%   $68.4486   $68.45   $68.45   $68.40  
  Purchase #2 $240.83   13.273%   $272.7954   $272.80   $272.80   $272.80  
  Purchase #3 $142.70   11.436%   $159.0192   $159.02   $159.00   $159.00  
  Purchase #4 $116.35   13.638%   $132.2178   $132.22   $132.20   $132.20  
  Purchase #5 $158.56   8.384%   $171.8537   $171.85   $171.85   $171.90  
  Purchase #6 $32.51   8.339%   $35.221   $35.22   $35.20   $35.20  
  Purchase #7 $207.33   5.781%   $219.3157   $219.32   $219.30   $219.30  
  7 purchase totals = $960.23       $1,058.8714   $1,058.88   $1,058.80   $1,058.80