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 $114.56   10.253%   $126.3058   $126.31   $126.30   $126.30  
  Purchase #2 $35.75   11.149%   $39.7358   $39.74   $39.75   $39.70  
  Purchase #3 $228.65   11.390%   $254.6932   $254.69   $254.70   $254.70  
  Purchase #4 $184.63   9.744%   $202.6203   $202.62   $202.60   $202.60  
  Purchase #5 $86.83   10.251%   $95.7309   $95.73   $95.75   $95.70  
  Purchase #6 $139.86   7.531%   $150.3929   $150.39   $150.40   $150.40  
  Purchase #7 $164.69   11.566%   $183.738   $183.74   $183.75   $183.70  
  7 purchase totals = $954.97       $1,053.2169   $1,053.22   $1,053.25   $1,053.10