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 $95.52   7.121%   $102.322   $102.32   $102.30   $102.30  
  Purchase #2 $43.69   11.361%   $48.6536   $48.65   $48.65   $48.70  
  Purchase #3 $43.37   5.257%   $45.65   $45.65   $45.65   $45.70  
  Purchase #4 $68.61   11.651%   $76.6038   $76.60   $76.60   $76.60  
  Purchase #5 $64.37   4.188%   $67.0658   $67.07   $67.05   $67.10  
  Purchase #6 $211.48   6.729%   $225.7105   $225.71   $225.70   $225.70  
  Purchase #7 $179.81   11.861%   $201.1373   $201.14   $201.15   $201.10  
  7 purchase totals = $706.85       $767.1430   $767.14   $767.10   $767.20