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 $74.27   4.409%   $77.5446   $77.54   $77.55   $77.50  
  Purchase #2 $109.51   4.278%   $114.1948   $114.19   $114.20   $114.20  
  Purchase #3 $6.72   5.266%   $7.0739   $7.07   $7.05   $7.10  
  Purchase #4 $174.29   4.626%   $182.3527   $182.35   $182.35   $182.40  
  Purchase #5 $181.96   13.560%   $206.6338   $206.63   $206.65   $206.60  
  Purchase #6 $205.47   12.594%   $231.3469   $231.35   $231.35   $231.30  
  Purchase #7 $50.53   9.331%   $55.245   $55.25   $55.25   $55.20  
  7 purchase totals = $802.75       $874.3917   $874.38   $874.40   $874.30