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 $61.81   12.754%   $69.6932   $69.69   $69.70   $69.70  
  Purchase #2 $120.97   4.282%   $126.1499   $126.15   $126.15   $126.10  
  Purchase #3 $200.43   6.281%   $213.019   $213.02   $213.00   $213.00  
  Purchase #4 $134.35   11.356%   $149.6068   $149.61   $149.60   $149.60  
  Purchase #5 $236.73   9.736%   $259.778   $259.78   $259.80   $259.80  
  Purchase #6 $93.46   6.384%   $99.4265   $99.43   $99.45   $99.40  
  Purchase #7 $207.41   11.587%   $231.4426   $231.44   $231.45   $231.40  
  7 purchase totals = $1,055.16       $1,149.1160   $1,149.12   $1,149.15   $1,149.00