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 $241.95   10.729%   $267.9088   $267.91   $267.90   $267.90  
  Purchase #2 $205.28   7.293%   $220.2511   $220.25   $220.25   $220.30  
  Purchase #3 $110.57   7.769%   $119.1602   $119.16   $119.15   $119.20  
  Purchase #4 $61.95   10.696%   $68.5762   $68.58   $68.60   $68.60  
  Purchase #5 $51.82   11.695%   $57.8803   $57.88   $57.90   $57.90  
  Purchase #6 $230.64   11.297%   $256.6954   $256.70   $256.70   $256.70  
  Purchase #7 $161.72   13.735%   $183.9322   $183.93   $183.95   $183.90  
  7 purchase totals = $1,063.93       $1,174.4042   $1,174.41   $1,174.45   $1,174.50