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 $120.60   4.275%   $125.7557   $125.76   $125.75   $125.80  
  Purchase #2 $180.60   11.685%   $201.7031   $201.70   $201.70   $201.70  
  Purchase #3 $99.97   13.286%   $113.252   $113.25   $113.25   $113.30  
  Purchase #4 $66.99   3.873%   $69.5845   $69.58   $69.60   $69.60  
  Purchase #5 $203.77   3.715%   $211.3401   $211.34   $211.35   $211.30  
  Purchase #6 $201.74   8.747%   $219.3862   $219.39   $219.40   $219.40  
  Purchase #7 $71.87   5.189%   $75.5993   $75.60   $75.60   $75.60  
  7 purchase totals = $945.54       $1,016.6209   $1,016.62   $1,016.65   $1,016.70