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 $63.85   9.414%   $69.8608   $69.86   $69.85   $69.90  
  Purchase #2 $191.84   3.565%   $198.6791   $198.68   $198.70   $198.70  
  Purchase #3 $159.77   5.236%   $168.1356   $168.14   $168.15   $168.10  
  Purchase #4 $12.66   5.739%   $13.3866   $13.39   $13.40   $13.40  
  Purchase #5 $32.92   10.590%   $36.4062   $36.41   $36.40   $36.40  
  Purchase #6 $205.61   8.828%   $223.7613   $223.76   $223.75   $223.80  
  Purchase #7 $63.66   4.222%   $66.3477   $66.35   $66.35   $66.30  
  7 purchase totals = $730.31       $776.5773   $776.59   $776.60   $776.60