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 $63.25   10.629%   $69.9728   $69.97   $69.95   $70.00  
  Purchase #2 $113.91   10.845%   $126.2635   $126.26   $126.25   $126.30  
  Purchase #3 $84.89   10.726%   $93.9953   $94.00   $94.00   $94.00  
  Purchase #4 $154.26   8.159%   $166.8461   $166.85   $166.85   $166.80  
  Purchase #5 $53.80   3.549%   $55.7094   $55.71   $55.70   $55.70  
  Purchase #6 $219.93   7.256%   $235.8881   $235.89   $235.90   $235.90  
  Purchase #7 $148.42   11.560%   $165.5774   $165.58   $165.60   $165.60  
  7 purchase totals = $838.46       $914.2526   $914.26   $914.25   $914.30