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 $235.64   11.577%   $262.92   $262.92   $262.90   $262.90  
  Purchase #2 $156.87   8.818%   $170.7028   $170.70   $170.70   $170.70  
  Purchase #3 $231.55   10.146%   $255.0431   $255.04   $255.05   $255.00  
  Purchase #4 $45.29   9.706%   $49.6858   $49.69   $49.70   $49.70  
  Purchase #5 $226.80   7.551%   $243.9257   $243.93   $243.95   $243.90  
  Purchase #6 $62.25   7.828%   $67.1229   $67.12   $67.10   $67.10  
  Purchase #7 $53.88   5.778%   $56.9932   $56.99   $57.00   $57.00  
  7 purchase totals = $1,012.28       $1,106.3935   $1,106.39   $1,106.40   $1,106.30