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 $108.94   8.821%   $118.5496   $118.55   $118.55   $118.50  
  Purchase #2 $212.81   8.327%   $230.5307   $230.53   $230.55   $230.50  
  Purchase #3 $117.61   8.336%   $127.414   $127.41   $127.40   $127.40  
  Purchase #4 $250.91   3.510%   $259.7169   $259.72   $259.70   $259.70  
  Purchase #5 $23.72   11.370%   $26.417   $26.42   $26.40   $26.40  
  Purchase #6 $165.28   7.399%   $177.5091   $177.51   $177.50   $177.50  
  Purchase #7 $212.39   10.636%   $234.9798   $234.98   $235.00   $235.00  
  7 purchase totals = $1,091.66       $1,175.1171   $1,175.12   $1,175.10   $1,175.00