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 $174.83   12.288%   $196.3131   $196.31   $196.30   $196.30  
  Purchase #2 $243.88   6.332%   $259.3225   $259.32   $259.30   $259.30  
  Purchase #3 $17.61   9.179%   $19.2264   $19.23   $19.25   $19.20  
  Purchase #4 $176.40   7.416%   $189.4818   $189.48   $189.50   $189.50  
  Purchase #5 $178.54   4.744%   $187.0099   $187.01   $187.00   $187.00  
  Purchase #6 $148.30   4.147%   $154.45   $154.45   $154.45   $154.50  
  Purchase #7 $23.52   13.646%   $26.7295   $26.73   $26.75   $26.70  
  7 purchase totals = $963.08       $1,032.5332   $1,032.53   $1,032.55   $1,032.50