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 $85.59   8.193%   $92.6024   $92.60   $92.60   $92.60  
  Purchase #2 $188.46   10.805%   $208.8231   $208.82   $208.80   $208.80  
  Purchase #3 $25.73   11.445%   $28.6748   $28.67   $28.65   $28.70  
  Purchase #4 $161.75   7.656%   $174.1336   $174.13   $174.15   $174.10  
  Purchase #5 $121.50   3.627%   $125.9068   $125.91   $125.90   $125.90  
  Purchase #6 $204.27   10.686%   $226.0983   $226.10   $226.10   $226.10  
  Purchase #7 $10.96   5.374%   $11.549   $11.55   $11.55   $11.50  
  7 purchase totals = $798.26       $867.7880   $867.78   $867.75   $867.70