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 $61.82   3.666%   $64.0863   $64.09   $64.10   $64.10  
  Purchase #2 $31.69   5.268%   $33.3594   $33.36   $33.35   $33.40  
  Purchase #3 $157.43   13.188%   $178.1919   $178.19   $178.20   $178.20  
  Purchase #4 $201.56   6.250%   $214.1575   $214.16   $214.15   $214.20  
  Purchase #5 $217.47   3.525%   $225.1358   $225.14   $225.15   $225.10  
  Purchase #6 $247.65   6.261%   $263.1554   $263.16   $263.15   $263.20  
  Purchase #7 $51.90   8.723%   $56.4272   $56.43   $56.45   $56.40  
  7 purchase totals = $969.52       $1,034.5135   $1,034.53   $1,034.55   $1,034.60