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 $162.37   3.240%   $167.6308   $167.63   $167.65   $167.60  
  Purchase #2 $91.41   5.415%   $96.3599   $96.36   $96.35   $96.40  
  Purchase #3 $118.37   12.864%   $133.5971   $133.60   $133.60   $133.60  
  Purchase #4 $197.50   11.581%   $220.3725   $220.37   $220.35   $220.40  
  Purchase #5 $183.66   4.838%   $192.5455   $192.55   $192.55   $192.50  
  Purchase #6 $235.65   5.431%   $248.4482   $248.45   $248.45   $248.40  
  Purchase #7 $177.43   13.515%   $201.4097   $201.41   $201.40   $201.40  
  7 purchase totals = $1,166.39       $1,260.3637   $1,260.37   $1,260.35   $1,260.30