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 $55.88   7.503%   $60.0727   $60.07   $60.05   $60.10  
  Purchase #2 $235.42   11.839%   $263.2914   $263.29   $263.30   $263.30  
  Purchase #3 $103.52   9.233%   $113.078   $113.08   $113.10   $113.10  
  Purchase #4 $155.66   3.844%   $161.6436   $161.64   $161.65   $161.60  
  Purchase #5 $243.75   8.449%   $264.3444   $264.34   $264.35   $264.30  
  Purchase #6 $74.79   4.523%   $78.1728   $78.17   $78.15   $78.20  
  Purchase #7 $69.70   5.797%   $73.7405   $73.74   $73.75   $73.70  
  7 purchase totals = $938.72       $1,014.3434   $1,014.33   $1,014.35   $1,014.30