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 $62.25   12.342%   $69.9329   $69.93   $69.95   $69.90  
  Purchase #2 $189.80   11.278%   $211.2056   $211.21   $211.20   $211.20  
  Purchase #3 $248.58   5.573%   $262.4334   $262.43   $262.45   $262.40  
  Purchase #4 $175.71   5.336%   $185.0859   $185.09   $185.10   $185.10  
  Purchase #5 $118.83   5.725%   $125.633   $125.63   $125.65   $125.60  
  Purchase #6 $229.31   11.450%   $255.566   $255.57   $255.55   $255.60  
  Purchase #7 $143.58   5.708%   $151.7755   $151.78   $151.80   $151.80  
  7 purchase totals = $1,168.06       $1,261.6323   $1,261.64   $1,261.70   $1,261.60