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 $33.82   12.592%   $38.0786   $38.08   $38.10   $38.10  
  Purchase #2 $193.89   6.652%   $206.7876   $206.79   $206.80   $206.80  
  Purchase #3 $200.77   8.438%   $217.711   $217.71   $217.70   $217.70  
  Purchase #4 $31.84   10.558%   $35.2017   $35.20   $35.20   $35.20  
  Purchase #5 $156.32   8.636%   $169.8198   $169.82   $169.80   $169.80  
  Purchase #6 $248.60   5.654%   $262.6558   $262.66   $262.65   $262.70  
  Purchase #7 $169.97   8.175%   $183.865   $183.87   $183.85   $183.90  
  7 purchase totals = $1,035.21       $1,114.1195   $1,114.13   $1,114.10   $1,114.20