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 $169.36   8.702%   $184.0977   $184.10   $184.10   $184.10  
  Purchase #2 $126.58   13.371%   $143.505   $143.51   $143.50   $143.50  
  Purchase #3 $208.90   5.540%   $220.4731   $220.47   $220.45   $220.50  
  Purchase #4 $175.91   12.435%   $197.7844   $197.78   $197.80   $197.80  
  Purchase #5 $55.94   3.323%   $57.7989   $57.80   $57.80   $57.80  
  Purchase #6 $181.50   11.535%   $202.436   $202.44   $202.45   $202.40  
  Purchase #7 $24.49   8.623%   $26.6018   $26.60   $26.60   $26.60  
  7 purchase totals = $942.68       $1,032.6969   $1,032.70   $1,032.70   $1,032.70