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 $114.29   4.412%   $119.3325   $119.33   $119.35   $119.30  
  Purchase #2 $157.98   3.848%   $164.0591   $164.06   $164.05   $164.10  
  Purchase #3 $210.58   7.793%   $226.9905   $226.99   $227.00   $227.00  
  Purchase #4 $49.85   8.746%   $54.2099   $54.21   $54.20   $54.20  
  Purchase #5 $98.57   5.304%   $103.7982   $103.80   $103.80   $103.80  
  Purchase #6 $187.41   11.314%   $208.6136   $208.61   $208.60   $208.60  
  Purchase #7 $181.27   6.538%   $193.1214   $193.12   $193.10   $193.10  
  7 purchase totals = $999.95       $1,070.1252   $1,070.12   $1,070.10   $1,070.10