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 $68.61   10.819%   $76.0329   $76.03   $76.05   $76.00  
  Purchase #2 $38.32   7.143%   $41.0572   $41.06   $41.05   $41.10  
  Purchase #3 $68.29   13.757%   $77.6847   $77.68   $77.70   $77.70  
  Purchase #4 $151.42   5.352%   $159.524   $159.52   $159.50   $159.50  
  Purchase #5 $192.59   11.623%   $214.9747   $214.97   $214.95   $215.00  
  Purchase #6 $53.35   5.136%   $56.0901   $56.09   $56.10   $56.10  
  Purchase #7 $219.80   12.820%   $247.9784   $247.98   $248.00   $248.00  
  7 purchase totals = $792.38       $873.3420   $873.33   $873.35   $873.40