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 $196.53   10.840%   $217.8339   $217.83   $217.85   $217.80  
  Purchase #2 $113.41   3.566%   $117.4542   $117.45   $117.45   $117.50  
  Purchase #3 $125.33   4.173%   $130.56   $130.56   $130.55   $130.60  
  Purchase #4 $113.88   11.244%   $126.6847   $126.68   $126.70   $126.70  
  Purchase #5 $228.32   13.185%   $258.424   $258.42   $258.40   $258.40  
  Purchase #6 $31.81   9.693%   $34.8933   $34.89   $34.90   $34.90  
  Purchase #7 $119.45   4.390%   $124.6939   $124.69   $124.70   $124.70  
  7 purchase totals = $928.73       $1,010.5440   $1,010.52   $1,010.55   $1,010.60