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 $68.62   5.409%   $72.3317   $72.33   $72.35   $72.30  
  Purchase #2 $134.57   8.236%   $145.6532   $145.65   $145.65   $145.70  
  Purchase #3 $42.74   11.464%   $47.6397   $47.64   $47.65   $47.60  
  Purchase #4 $241.32   5.262%   $254.0183   $254.02   $254.00   $254.00  
  Purchase #5 $248.95   5.734%   $263.2248   $263.22   $263.20   $263.20  
  Purchase #6 $137.47   7.661%   $148.0016   $148.00   $148.00   $148.00  
  Purchase #7 $249.79   9.713%   $274.0521   $274.05   $274.05   $274.10  
  7 purchase totals = $1,123.46       $1,204.9214   $1,204.91   $1,204.90   $1,204.90