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 $71.45   3.493%   $73.9457   $73.95   $73.95   $73.90  
  Purchase #2 $76.52   10.265%   $84.3748   $84.37   $84.35   $84.40  
  Purchase #3 $93.43   13.576%   $106.1141   $106.11   $106.10   $106.10  
  Purchase #4 $113.73   10.773%   $125.9821   $125.98   $126.00   $126.00  
  Purchase #5 $232.29   13.754%   $264.2392   $264.24   $264.25   $264.20  
  Purchase #6 $177.34   13.451%   $201.194   $201.19   $201.20   $201.20  
  Purchase #7 $72.84   6.662%   $77.6926   $77.69   $77.70   $77.70  
  7 purchase totals = $837.60       $933.5425   $933.53   $933.55   $933.50