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 $70.69   7.538%   $76.0186   $76.02   $76.00   $76.00  
  Purchase #2 $69.58   4.311%   $72.5796   $72.58   $72.60   $72.60  
  Purchase #3 $39.31   12.747%   $44.3208   $44.32   $44.30   $44.30  
  Purchase #4 $146.99   10.684%   $162.6944   $162.69   $162.70   $162.70  
  Purchase #5 $137.89   5.448%   $145.4022   $145.40   $145.40   $145.40  
  Purchase #6 $142.68   8.494%   $154.7992   $154.80   $154.80   $154.80  
  Purchase #7 $108.83   4.350%   $113.5641   $113.56   $113.55   $113.60  
  7 purchase totals = $715.97       $769.3789   $769.37   $769.35   $769.40