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 $210.93   7.383%   $226.503   $226.50   $226.50   $226.50  
  Purchase #2 $62.88   13.403%   $71.3078   $71.31   $71.30   $71.30  
  Purchase #3 $127.36   13.464%   $144.5078   $144.51   $144.50   $144.50  
  Purchase #4 $235.84   9.284%   $257.7354   $257.74   $257.75   $257.70  
  Purchase #5 $75.80   10.232%   $83.5559   $83.56   $83.55   $83.60  
  Purchase #6 $226.87   8.429%   $245.9929   $245.99   $246.00   $246.00  
  Purchase #7 $79.35   9.451%   $86.8494   $86.85   $86.85   $86.80  
  7 purchase totals = $1,019.03       $1,116.4522   $1,116.46   $1,116.45   $1,116.40