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 $241.68   10.874%   $267.9603   $267.96   $267.95   $268.00  
  Purchase #2 $138.40   4.853%   $145.1166   $145.12   $145.10   $145.10  
  Purchase #3 $33.40   5.279%   $35.1632   $35.16   $35.15   $35.20  
  Purchase #4 $158.62   9.795%   $174.1568   $174.16   $174.15   $174.20  
  Purchase #5 $249.64   6.829%   $266.6879   $266.69   $266.70   $266.70  
  Purchase #6 $134.59   12.604%   $151.5537   $151.55   $151.55   $151.60  
  Purchase #7 $65.51   4.355%   $68.363   $68.36   $68.35   $68.40  
  7 purchase totals = $1,021.84       $1,109.0015   $1,109.00   $1,108.95   $1,109.20