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 $90.58   4.797%   $94.9251   $94.93   $94.95   $94.90  
  Purchase #2 $25.34   13.153%   $28.673   $28.67   $28.65   $28.70  
  Purchase #3 $25.92   8.385%   $28.0934   $28.09   $28.10   $28.10  
  Purchase #4 $165.64   4.835%   $173.6487   $173.65   $173.65   $173.60  
  Purchase #5 $212.70   12.292%   $238.8451   $238.85   $238.85   $238.80  
  Purchase #6 $198.27   7.509%   $213.1581   $213.16   $213.15   $213.20  
  Purchase #7 $202.99   7.276%   $217.7596   $217.76   $217.75   $217.80  
  7 purchase totals = $921.44       $995.1030   $995.11   $995.10   $995.10