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 $61.95   12.229%   $69.5259   $69.53   $69.55   $69.50  
  Purchase #2 $106.50   10.767%   $117.9669   $117.97   $117.95   $118.00  
  Purchase #3 $15.61   4.509%   $16.3139   $16.31   $16.30   $16.30  
  Purchase #4 $241.42   7.447%   $259.3985   $259.40   $259.40   $259.40  
  Purchase #5 $233.77   10.196%   $257.6052   $257.61   $257.60   $257.60  
  Purchase #6 $193.80   10.244%   $213.6529   $213.65   $213.65   $213.70  
  Purchase #7 $170.44   6.618%   $181.7197   $181.72   $181.70   $181.70  
  7 purchase totals = $1,023.49       $1,116.1830   $1,116.19   $1,116.15   $1,116.20