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 $114.75   10.541%   $126.8458   $126.85   $126.85   $126.80  
  Purchase #2 $144.30   4.344%   $150.5684   $150.57   $150.55   $150.60  
  Purchase #3 $123.93   6.213%   $131.6298   $131.63   $131.65   $131.60  
  Purchase #4 $236.53   13.407%   $268.2416   $268.24   $268.25   $268.20  
  Purchase #5 $110.92   11.425%   $123.5926   $123.59   $123.60   $123.60  
  Purchase #6 $115.89   7.719%   $124.8355   $124.84   $124.85   $124.80  
  Purchase #7 $170.72   3.656%   $176.9615   $176.96   $176.95   $177.00  
  7 purchase totals = $1,017.04       $1,102.6752   $1,102.68   $1,102.70   $1,102.60