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 $194.33   3.527%   $201.184   $201.18   $201.20   $201.20  
  Purchase #2 $146.46   12.717%   $165.0853   $165.09   $165.10   $165.10  
  Purchase #3 $60.46   8.285%   $65.4691   $65.47   $65.45   $65.50  
  Purchase #4 $158.63   12.439%   $178.362   $178.36   $178.35   $178.40  
  Purchase #5 $181.73   10.162%   $200.1974   $200.20   $200.20   $200.20  
  Purchase #6 $114.89   12.549%   $129.3075   $129.31   $129.30   $129.30  
  Purchase #7 $100.90   8.659%   $109.6369   $109.64   $109.65   $109.60  
  7 purchase totals = $957.40       $1,049.2422   $1,049.25   $1,049.25   $1,049.30