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 $241.62   4.731%   $253.051   $253.05   $253.05   $253.10  
  Purchase #2 $160.62   11.869%   $179.684   $179.68   $179.70   $179.70  
  Purchase #3 $83.65   6.351%   $88.9626   $88.96   $88.95   $89.00  
  Purchase #4 $147.77   4.432%   $154.3192   $154.32   $154.30   $154.30  
  Purchase #5 $31.71   5.803%   $33.5501   $33.55   $33.55   $33.60  
  Purchase #6 $211.69   11.482%   $235.9962   $236.00   $236.00   $236.00  
  Purchase #7 $147.69   12.545%   $166.2177   $166.22   $166.20   $166.20  
  7 purchase totals = $1,024.75       $1,111.7808   $1,111.78   $1,111.75   $1,111.90