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 $31.47   7.819%   $33.9306   $33.93   $33.95   $33.90  
  Purchase #2 $199.89   3.135%   $206.1566   $206.16   $206.15   $206.20  
  Purchase #3 $125.34   3.220%   $129.3759   $129.38   $129.40   $129.40  
  Purchase #4 $235.34   5.441%   $248.1448   $248.14   $248.15   $248.10  
  Purchase #5 $197.54   10.818%   $218.9099   $218.91   $218.90   $218.90  
  Purchase #6 $130.59   4.103%   $135.9481   $135.95   $135.95   $135.90  
  Purchase #7 $154.78   4.536%   $161.8008   $161.80   $161.80   $161.80  
  7 purchase totals = $1,074.95       $1,134.2667   $1,134.27   $1,134.30   $1,134.20