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 $122.50   9.540%   $134.1865   $134.19   $134.20   $134.20  
  Purchase #2 $214.48   6.619%   $228.6764   $228.68   $228.70   $228.70  
  Purchase #3 $97.37   5.589%   $102.812   $102.81   $102.80   $102.80  
  Purchase #4 $160.51   9.859%   $176.3347   $176.33   $176.35   $176.30  
  Purchase #5 $147.96   9.621%   $162.1952   $162.20   $162.20   $162.20  
  Purchase #6 $48.90   10.291%   $53.9323   $53.93   $53.95   $53.90  
  Purchase #7 $233.97   8.375%   $253.565   $253.57   $253.55   $253.60  
  7 purchase totals = $1,025.69       $1,111.7021   $1,111.71   $1,111.75   $1,111.70