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 $182.78   8.252%   $197.863   $197.86   $197.85   $197.90  
  Purchase #2 $135.85   5.783%   $143.7062   $143.71   $143.70   $143.70  
  Purchase #3 $72.67   4.815%   $76.1691   $76.17   $76.15   $76.20  
  Purchase #4 $52.32   9.549%   $57.316   $57.32   $57.30   $57.30  
  Purchase #5 $219.45   10.753%   $243.0475   $243.05   $243.05   $243.00  
  Purchase #6 $142.55   4.366%   $148.7737   $148.77   $148.75   $148.80  
  Purchase #7 $26.48   9.838%   $29.0851   $29.09   $29.10   $29.10  
  7 purchase totals = $832.10       $895.9606   $895.97   $895.90   $896.00