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 $238.99   9.860%   $262.5544   $262.55   $262.55   $262.60  
  Purchase #2 $145.78   4.563%   $152.4319   $152.43   $152.45   $152.40  
  Purchase #3 $201.44   5.512%   $212.5434   $212.54   $212.55   $212.50  
  Purchase #4 $58.55   3.494%   $60.5957   $60.60   $60.60   $60.60  
  Purchase #5 $179.43   12.571%   $201.9861   $201.99   $202.00   $202.00  
  Purchase #6 $195.88   4.103%   $203.917   $203.92   $203.90   $203.90  
  Purchase #7 $16.26   7.744%   $17.5192   $17.52   $17.50   $17.50  
  7 purchase totals = $1,036.33       $1,111.5477   $1,111.55   $1,111.55   $1,111.50