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 $196.75   5.548%   $207.6657   $207.67   $207.65   $207.70  
  Purchase #2 $137.75   13.373%   $156.1713   $156.17   $156.15   $156.20  
  Purchase #3 $137.42   4.395%   $143.4596   $143.46   $143.45   $143.50  
  Purchase #4 $34.65   4.108%   $36.0734   $36.07   $36.05   $36.10  
  Purchase #5 $27.66   6.732%   $29.5221   $29.52   $29.50   $29.50  
  Purchase #6 $141.34   8.308%   $153.0825   $153.08   $153.10   $153.10  
  Purchase #7 $197.67   5.280%   $208.107   $208.11   $208.10   $208.10  
  7 purchase totals = $873.24       $934.0816   $934.08   $934.00   $934.20