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 $167.29   11.674%   $186.8194   $186.82   $186.80   $186.80  
  Purchase #2 $149.96   3.209%   $154.7722   $154.77   $154.75   $154.80  
  Purchase #3 $85.56   10.724%   $94.7355   $94.74   $94.75   $94.70  
  Purchase #4 $45.45   5.711%   $48.0456   $48.05   $48.05   $48.00  
  Purchase #5 $159.96   8.149%   $172.9951   $173.00   $173.00   $173.00  
  Purchase #6 $247.42   4.687%   $259.0166   $259.02   $259.00   $259.00  
  Purchase #7 $166.80   7.380%   $179.1098   $179.11   $179.10   $179.10  
  7 purchase totals = $1,022.44       $1,095.4942   $1,095.51   $1,095.45   $1,095.40