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 $46.93   11.318%   $52.2415   $52.24   $52.25   $52.20  
  Purchase #2 $203.42   8.413%   $220.5337   $220.53   $220.55   $220.50  
  Purchase #3 $41.88   3.608%   $43.391   $43.39   $43.40   $43.40  
  Purchase #4 $184.33   8.772%   $200.4994   $200.50   $200.50   $200.50  
  Purchase #5 $34.30   10.410%   $37.8706   $37.87   $37.85   $37.90  
  Purchase #6 $218.70   7.327%   $234.7241   $234.72   $234.70   $234.70  
  Purchase #7 $210.60   12.431%   $236.7797   $236.78   $236.80   $236.80  
  7 purchase totals = $940.16       $1,026.0400   $1,026.03   $1,026.05   $1,026.00