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 $43.66   10.198%   $48.1124   $48.11   $48.10   $48.10  
  Purchase #2 $201.55   6.378%   $214.4049   $214.40   $214.40   $214.40  
  Purchase #3 $172.68   5.659%   $182.452   $182.45   $182.45   $182.50  
  Purchase #4 $31.51   11.170%   $35.0297   $35.03   $35.05   $35.00  
  Purchase #5 $176.72   13.814%   $201.1321   $201.13   $201.15   $201.10  
  Purchase #6 $168.92   5.344%   $177.9471   $177.95   $177.95   $177.90  
  Purchase #7 $165.32   13.388%   $187.453   $187.45   $187.45   $187.50  
  7 purchase totals = $960.36       $1,046.5312   $1,046.52   $1,046.55   $1,046.50