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 $162.58   8.813%   $176.9082   $176.91   $176.90   $176.90  
  Purchase #2 $55.26   9.650%   $60.5926   $60.59   $60.60   $60.60  
  Purchase #3 $192.92   9.668%   $211.5715   $211.57   $211.55   $211.60  
  Purchase #4 $112.58   13.399%   $127.6646   $127.66   $127.65   $127.70  
  Purchase #5 $46.68   6.159%   $49.555   $49.56   $49.55   $49.60  
  Purchase #6 $163.60   7.689%   $176.1792   $176.18   $176.20   $176.20  
  Purchase #7 $152.37   6.193%   $161.8063   $161.81   $161.80   $161.80  
  7 purchase totals = $885.99       $964.2774   $964.28   $964.25   $964.40