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 $184.26   9.236%   $201.2783   $201.28   $201.30   $201.30  
  Purchase #2 $174.99   12.606%   $197.0492   $197.05   $197.05   $197.00  
  Purchase #3 $142.81   8.381%   $154.7789   $154.78   $154.80   $154.80  
  Purchase #4 $78.66   11.597%   $87.7822   $87.78   $87.80   $87.80  
  Purchase #5 $80.94   13.191%   $91.6168   $91.62   $91.60   $91.60  
  Purchase #6 $119.51   13.844%   $136.055   $136.06   $136.05   $136.10  
  Purchase #7 $162.29   3.156%   $167.4119   $167.41   $167.40   $167.40  
  7 purchase totals = $943.46       $1,035.9723   $1,035.98   $1,036.00   $1,036.00