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 $58.94   5.249%   $62.0338   $62.03   $62.05   $62.00  
  Purchase #2 $228.90   4.558%   $239.3333   $239.33   $239.35   $239.30  
  Purchase #3 $147.60   8.586%   $160.2729   $160.27   $160.25   $160.30  
  Purchase #4 $168.26   11.572%   $187.731   $187.73   $187.75   $187.70  
  Purchase #5 $208.97   4.393%   $218.1501   $218.15   $218.15   $218.20  
  Purchase #6 $125.74   13.454%   $142.6571   $142.66   $142.65   $142.70  
  Purchase #7 $131.56   11.252%   $146.3631   $146.36   $146.35   $146.40  
  7 purchase totals = $1,069.97       $1,156.5413   $1,156.53   $1,156.55   $1,156.60