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 $65.83   5.409%   $69.3907   $69.39   $69.40   $69.40  
  Purchase #2 $177.83   5.341%   $187.3279   $187.33   $187.35   $187.30  
  Purchase #3 $206.60   13.174%   $233.8175   $233.82   $233.80   $233.80  
  Purchase #4 $77.26   5.650%   $81.6252   $81.63   $81.65   $81.60  
  Purchase #5 $46.55   5.823%   $49.2606   $49.26   $49.25   $49.30  
  Purchase #6 $64.74   13.270%   $73.331   $73.33   $73.35   $73.30  
  Purchase #7 $183.95   7.645%   $198.013   $198.01   $198.00   $198.00  
  7 purchase totals = $822.76       $892.7659   $892.77   $892.80   $892.70