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 $69.58   7.535%   $74.8229   $74.82   $74.80   $74.80  
  Purchase #2 $53.93   8.116%   $58.307   $58.31   $58.30   $58.30  
  Purchase #3 $81.76   7.535%   $87.9206   $87.92   $87.90   $87.90  
  Purchase #4 $41.85   4.865%   $43.886   $43.89   $43.90   $43.90  
  Purchase #5 $50.83   10.573%   $56.2043   $56.20   $56.20   $56.20  
  Purchase #6 $205.29   13.389%   $232.7763   $232.78   $232.80   $232.80  
  Purchase #7 $58.52   3.298%   $60.45   $60.45   $60.45   $60.50  
  7 purchase totals = $561.76       $614.3671   $614.37   $614.35   $614.40