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 $181.80   8.763%   $197.7311   $197.73   $197.75   $197.70  
  Purchase #2 $70.72   4.492%   $73.8967   $73.90   $73.90   $73.90  
  Purchase #3 $250.48   5.820%   $265.0579   $265.06   $265.05   $265.10  
  Purchase #4 $208.58   11.385%   $232.3268   $232.33   $232.35   $232.30  
  Purchase #5 $246.30   8.156%   $266.3882   $266.39   $266.40   $266.40  
  Purchase #6 $57.73   11.370%   $64.2939   $64.29   $64.30   $64.30  
  Purchase #7 $106.88   8.862%   $116.3517   $116.35   $116.35   $116.40  
  7 purchase totals = $1,122.49       $1,216.0463   $1,216.05   $1,216.10   $1,216.10