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 $58.38   7.366%   $62.6803   $62.68   $62.70   $62.70  
  Purchase #2 $153.84   10.735%   $170.3547   $170.35   $170.35   $170.40  
  Purchase #3 $220.64   6.701%   $235.4251   $235.43   $235.45   $235.40  
  Purchase #4 $221.27   13.595%   $251.3517   $251.35   $251.35   $251.40  
  Purchase #5 $201.25   3.557%   $208.4085   $208.41   $208.40   $208.40  
  Purchase #6 $90.59   11.363%   $100.8837   $100.88   $100.90   $100.90  
  Purchase #7 $17.93   4.827%   $18.7955   $18.80   $18.80   $18.80  
  7 purchase totals = $963.90       $1,047.8995   $1,047.90   $1,047.95   $1,048.00