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 $58.68   5.104%   $61.675   $61.68   $61.70   $61.70  
  Purchase #2 $250.85   3.592%   $259.8605   $259.86   $259.85   $259.90  
  Purchase #3 $116.91   8.457%   $126.7971   $126.80   $126.80   $126.80  
  Purchase #4 $70.36   5.672%   $74.3508   $74.35   $74.35   $74.40  
  Purchase #5 $47.80   11.324%   $53.2129   $53.21   $53.20   $53.20  
  Purchase #6 $219.38   10.421%   $242.2416   $242.24   $242.25   $242.20  
  Purchase #7 $233.34   7.774%   $251.4799   $251.48   $251.50   $251.50  
  7 purchase totals = $997.32       $1,069.6178   $1,069.62   $1,069.65   $1,069.70