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 $88.78   6.565%   $94.6084   $94.61   $94.60   $94.60  
  Purchase #2 $204.42   13.601%   $232.2232   $232.22   $232.20   $232.20  
  Purchase #3 $57.99   8.407%   $62.8652   $62.87   $62.85   $62.90  
  Purchase #4 $204.82   13.616%   $232.7083   $232.71   $232.70   $232.70  
  Purchase #5 $161.70   6.162%   $171.664   $171.66   $171.65   $171.70  
  Purchase #6 $231.64   6.157%   $245.9021   $245.90   $245.90   $245.90  
  Purchase #7 $134.26   5.752%   $141.9826   $141.98   $142.00   $142.00  
  7 purchase totals = $1,083.61       $1,181.9538   $1,181.95   $1,181.90   $1,182.00