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 $43.97   10.547%   $48.6075   $48.61   $48.60   $48.60  
  Purchase #2 $189.77   6.814%   $202.7009   $202.70   $202.70   $202.70  
  Purchase #3 $84.58   10.287%   $93.2807   $93.28   $93.30   $93.30  
  Purchase #4 $224.85   13.755%   $255.7781   $255.78   $255.80   $255.80  
  Purchase #5 $213.63   6.182%   $226.8366   $226.84   $226.85   $226.80  
  Purchase #6 $141.73   11.234%   $157.6519   $157.65   $157.65   $157.70  
  Purchase #7 $24.75   5.587%   $26.1328   $26.13   $26.15   $26.10  
  7 purchase totals = $923.28       $1,010.9885   $1,010.99   $1,011.05   $1,011.00