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 $61.25   7.219%   $65.6716   $65.67   $65.65   $65.70  
  Purchase #2 $191.44   7.372%   $205.553   $205.55   $205.55   $205.60  
  Purchase #3 $44.74   3.247%   $46.1927   $46.19   $46.20   $46.20  
  Purchase #4 $209.65   11.806%   $234.4013   $234.40   $234.40   $234.40  
  Purchase #5 $143.61   13.188%   $162.5493   $162.55   $162.55   $162.50  
  Purchase #6 $82.29   3.171%   $84.8994   $84.90   $84.90   $84.90  
  Purchase #7 $31.70   12.747%   $35.7408   $35.74   $35.75   $35.70  
  7 purchase totals = $764.68       $835.0081   $835.00   $835.00   $835.00