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 $63.35   6.214%   $67.2866   $67.29   $67.30   $67.30  
  Purchase #2 $189.30   8.116%   $204.6636   $204.66   $204.65   $204.70  
  Purchase #3 $13.71   4.747%   $14.3608   $14.36   $14.35   $14.40  
  Purchase #4 $211.90   13.163%   $239.7924   $239.79   $239.80   $239.80  
  Purchase #5 $247.98   11.623%   $276.8027   $276.80   $276.80   $276.80  
  Purchase #6 $108.81   5.328%   $114.6074   $114.61   $114.60   $114.60  
  Purchase #7 $133.75   5.446%   $141.034   $141.03   $141.05   $141.00  
  7 purchase totals = $968.80       $1,058.5475   $1,058.54   $1,058.55   $1,058.60