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 $89.65   4.477%   $93.6636   $93.66   $93.65   $93.70  
  Purchase #2 $241.99   4.145%   $252.0205   $252.02   $252.00   $252.00  
  Purchase #3 $102.26   10.568%   $113.0668   $113.07   $113.05   $113.10  
  Purchase #4 $198.79   4.608%   $207.9502   $207.95   $207.95   $208.00  
  Purchase #5 $50.94   10.279%   $56.1761   $56.18   $56.20   $56.20  
  Purchase #6 $118.69   6.707%   $126.6505   $126.65   $126.65   $126.70  
  Purchase #7 $201.93   11.608%   $225.37   $225.37   $225.35   $225.40  
  7 purchase totals = $1,004.25       $1,074.8977   $1,074.90   $1,074.85   $1,075.10