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 $85.98   11.566%   $95.9244   $95.92   $95.90   $95.90  
  Purchase #2 $184.45   4.728%   $193.1708   $193.17   $193.15   $193.20  
  Purchase #3 $165.38   4.396%   $172.6501   $172.65   $172.65   $172.70  
  Purchase #4 $33.98   11.647%   $37.9377   $37.94   $37.95   $37.90  
  Purchase #5 $231.56   8.731%   $251.7775   $251.78   $251.80   $251.80  
  Purchase #6 $46.91   3.804%   $48.6945   $48.69   $48.70   $48.70  
  Purchase #7 $130.67   8.399%   $141.645   $141.65   $141.65   $141.60  
  7 purchase totals = $878.93       $941.8000   $941.80   $941.80   $941.80