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 $56.44   8.545%   $61.2628   $61.26   $61.25   $61.30  
  Purchase #2 $158.95   11.456%   $177.1593   $177.16   $177.15   $177.20  
  Purchase #3 $152.66   3.748%   $158.3817   $158.38   $158.40   $158.40  
  Purchase #4 $25.92   4.449%   $27.0732   $27.07   $27.05   $27.10  
  Purchase #5 $249.82   5.754%   $264.1946   $264.19   $264.20   $264.20  
  Purchase #6 $194.58   12.764%   $219.4162   $219.42   $219.40   $219.40  
  Purchase #7 $196.83   7.221%   $211.0431   $211.04   $211.05   $211.00  
  7 purchase totals = $1,035.20       $1,118.5309   $1,118.52   $1,118.50   $1,118.60