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 $117.29   7.526%   $126.1172   $126.12   $126.10   $126.10  
  Purchase #2 $239.52   10.237%   $264.0397   $264.04   $264.05   $264.00  
  Purchase #3 $87.54   7.126%   $93.7781   $93.78   $93.80   $93.80  
  Purchase #4 $137.87   4.130%   $143.564   $143.56   $143.55   $143.60  
  Purchase #5 $158.58   10.829%   $175.7526   $175.75   $175.75   $175.80  
  Purchase #6 $25.70   3.716%   $26.655   $26.66   $26.65   $26.70  
  Purchase #7 $151.69   13.639%   $172.379   $172.38   $172.40   $172.40  
  7 purchase totals = $918.19       $1,002.2856   $1,002.29   $1,002.30   $1,002.40