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 $215.83   13.318%   $244.5742   $244.57   $244.55   $244.60  
  Purchase #2 $32.86   10.129%   $36.1884   $36.19   $36.20   $36.20  
  Purchase #3 $237.44   6.214%   $252.1945   $252.19   $252.20   $252.20  
  Purchase #4 $105.31   10.385%   $116.2464   $116.25   $116.25   $116.20  
  Purchase #5 $133.69   3.271%   $138.063   $138.06   $138.05   $138.10  
  Purchase #6 $140.88   10.412%   $155.5484   $155.55   $155.55   $155.50  
  Purchase #7 $202.35   11.682%   $225.9885   $225.99   $226.00   $226.00  
  7 purchase totals = $1,068.36       $1,168.8034   $1,168.80   $1,168.80   $1,168.80