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 $104.27   9.371%   $114.0411   $114.04   $114.05   $114.00  
  Purchase #2 $79.74   11.344%   $88.7857   $88.79   $88.80   $88.80  
  Purchase #3 $172.51   4.118%   $179.614   $179.61   $179.60   $179.60  
  Purchase #4 $96.95   4.259%   $101.0791   $101.08   $101.10   $101.10  
  Purchase #5 $60.80   8.866%   $66.1905   $66.19   $66.20   $66.20  
  Purchase #6 $222.28   8.570%   $241.3294   $241.33   $241.35   $241.30  
  Purchase #7 $224.70   4.730%   $235.3283   $235.33   $235.35   $235.30  
  7 purchase totals = $961.25       $1,026.3681   $1,026.37   $1,026.45   $1,026.30