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 $151.40   6.469%   $161.1941   $161.19   $161.20   $161.20  
  Purchase #2 $167.87   4.632%   $175.6457   $175.65   $175.65   $175.60  
  Purchase #3 $139.64   12.410%   $156.9693   $156.97   $156.95   $157.00  
  Purchase #4 $222.89   11.612%   $248.772   $248.77   $248.75   $248.80  
  Purchase #5 $32.80   6.321%   $34.8733   $34.87   $34.85   $34.90  
  Purchase #6 $57.98   6.112%   $61.5237   $61.52   $61.50   $61.50  
  Purchase #7 $50.49   11.385%   $56.2383   $56.24   $56.25   $56.20  
  7 purchase totals = $823.07       $895.2164   $895.21   $895.15   $895.20