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 $196.89   7.351%   $211.3634   $211.36   $211.35   $211.40  
  Purchase #2 $66.29   10.457%   $73.2219   $73.22   $73.20   $73.20  
  Purchase #3 $106.58   12.219%   $119.603   $119.60   $119.60   $119.60  
  Purchase #4 $24.68   6.406%   $26.261   $26.26   $26.25   $26.30  
  Purchase #5 $140.81   7.277%   $151.0567   $151.06   $151.05   $151.10  
  Purchase #6 $208.91   8.367%   $226.3895   $226.39   $226.40   $226.40  
  Purchase #7 $194.52   3.729%   $201.7737   $201.77   $201.75   $201.80  
  7 purchase totals = $938.68       $1,009.6692   $1,009.66   $1,009.60   $1,009.80