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 $82.67   13.872%   $94.138   $94.14   $94.15   $94.10  
  Purchase #2 $49.88   8.707%   $54.2231   $54.22   $54.20   $54.20  
  Purchase #3 $189.66   9.185%   $207.0803   $207.08   $207.10   $207.10  
  Purchase #4 $169.49   11.183%   $188.4441   $188.44   $188.45   $188.40  
  Purchase #5 $173.34   10.666%   $191.8284   $191.83   $191.85   $191.80  
  Purchase #6 $208.79   8.707%   $226.9693   $226.97   $226.95   $227.00  
  Purchase #7 $198.86   6.353%   $211.4936   $211.49   $211.50   $211.50  
  7 purchase totals = $1,072.69       $1,174.1768   $1,174.17   $1,174.20   $1,174.10