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 $171.99   13.163%   $194.629   $194.63   $194.65   $194.60  
  Purchase #2 $24.59   3.279%   $25.3963   $25.40   $25.40   $25.40  
  Purchase #3 $151.37   3.202%   $156.2169   $156.22   $156.20   $156.20  
  Purchase #4 $162.72   12.366%   $182.842   $182.84   $182.85   $182.80  
  Purchase #5 $223.51   9.175%   $244.017   $244.02   $244.00   $244.00  
  Purchase #6 $45.63   12.751%   $51.4483   $51.45   $51.45   $51.40  
  Purchase #7 $201.54   3.305%   $208.2009   $208.20   $208.20   $208.20  
  7 purchase totals = $981.35       $1,062.7504   $1,062.76   $1,062.75   $1,062.60