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 $59.95   9.580%   $65.6932   $65.69   $65.70   $65.70  
  Purchase #2 $241.73   4.558%   $252.7481   $252.75   $252.75   $252.70  
  Purchase #3 $111.57   13.125%   $126.2136   $126.21   $126.20   $126.20  
  Purchase #4 $40.73   13.171%   $46.0945   $46.09   $46.10   $46.10  
  Purchase #5 $187.63   8.480%   $203.541   $203.54   $203.55   $203.50  
  Purchase #6 $132.90   7.847%   $143.3287   $143.33   $143.35   $143.30  
  Purchase #7 $164.74   7.640%   $177.3261   $177.33   $177.35   $177.30  
  7 purchase totals = $939.25       $1,014.9452   $1,014.94   $1,015.00   $1,014.80