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 $198.27   3.411%   $205.033   $205.03   $205.05   $205.00  
  Purchase #2 $198.87   3.717%   $206.262   $206.26   $206.25   $206.30  
  Purchase #3 $228.55   5.579%   $241.3008   $241.30   $241.30   $241.30  
  Purchase #4 $97.60   9.501%   $106.873   $106.87   $106.85   $106.90  
  Purchase #5 $205.49   9.468%   $224.9458   $224.95   $224.95   $224.90  
  Purchase #6 $169.43   4.556%   $177.1492   $177.15   $177.15   $177.10  
  Purchase #7 $72.84   13.773%   $82.8723   $82.87   $82.85   $82.90  
  7 purchase totals = $1,171.05       $1,244.4361   $1,244.43   $1,244.40   $1,244.40