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 $118.47   5.347%   $124.8046   $124.80   $124.80   $124.80  
  Purchase #2 $32.87   7.142%   $35.2176   $35.22   $35.20   $35.20  
  Purchase #3 $133.40   6.544%   $142.1297   $142.13   $142.15   $142.10  
  Purchase #4 $177.38   13.580%   $201.4682   $201.47   $201.45   $201.50  
  Purchase #5 $66.49   11.121%   $73.8844   $73.88   $73.90   $73.90  
  Purchase #6 $214.76   9.839%   $235.8902   $235.89   $235.90   $235.90  
  Purchase #7 $203.85   9.561%   $223.3401   $223.34   $223.35   $223.30  
  7 purchase totals = $947.22       $1,036.7348   $1,036.73   $1,036.75   $1,036.70