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 $56.35   7.275%   $60.4495   $60.45   $60.45   $60.40  
  Purchase #2 $179.81   8.300%   $194.7342   $194.73   $194.75   $194.70  
  Purchase #3 $153.62   5.866%   $162.6313   $162.63   $162.65   $162.60  
  Purchase #4 $30.76   9.619%   $33.7188   $33.72   $33.70   $33.70  
  Purchase #5 $196.71   4.288%   $205.1449   $205.14   $205.15   $205.10  
  Purchase #6 $249.55   5.771%   $263.9515   $263.95   $263.95   $264.00  
  Purchase #7 $217.57   6.532%   $231.7817   $231.78   $231.80   $231.80  
  7 purchase totals = $1,084.37       $1,152.4119   $1,152.40   $1,152.45   $1,152.30