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 $60.64   3.257%   $62.615   $62.62   $62.60   $62.60  
  Purchase #2 $238.94   5.643%   $252.4234   $252.42   $252.40   $252.40  
  Purchase #3 $123.38   5.413%   $130.0586   $130.06   $130.05   $130.10  
  Purchase #4 $93.39   11.546%   $104.1728   $104.17   $104.15   $104.20  
  Purchase #5 $185.71   10.387%   $204.9997   $205.00   $205.00   $205.00  
  Purchase #6 $209.59   10.749%   $232.1188   $232.12   $232.10   $232.10  
  Purchase #7 $50.73   5.183%   $53.3593   $53.36   $53.35   $53.40  
  7 purchase totals = $962.38       $1,039.7476   $1,039.75   $1,039.65   $1,039.80