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 $73.91   3.411%   $76.4311   $76.43   $76.45   $76.40  
  Purchase #2 $204.78   4.375%   $213.7391   $213.74   $213.75   $213.70  
  Purchase #3 $41.27   4.325%   $43.0549   $43.05   $43.05   $43.10  
  Purchase #4 $216.60   11.873%   $242.3169   $242.32   $242.30   $242.30  
  Purchase #5 $155.92   11.762%   $174.2593   $174.26   $174.25   $174.30  
  Purchase #6 $237.83   5.677%   $251.3316   $251.33   $251.35   $251.30  
  Purchase #7 $43.35   5.380%   $45.6822   $45.68   $45.70   $45.70  
  7 purchase totals = $973.66       $1,046.8151   $1,046.81   $1,046.85   $1,046.80