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 $243.82   6.369%   $259.3489   $259.35   $259.35   $259.30  
  Purchase #2 $213.58   10.255%   $235.4826   $235.48   $235.50   $235.50  
  Purchase #3 $122.46   7.608%   $131.7768   $131.78   $131.80   $131.80  
  Purchase #4 $18.97   12.423%   $21.3266   $21.33   $21.35   $21.30  
  Purchase #5 $211.29   10.124%   $232.681   $232.68   $232.70   $232.70  
  Purchase #6 $49.92   9.508%   $54.6664   $54.67   $54.65   $54.70  
  Purchase #7 $151.42   5.451%   $159.6739   $159.67   $159.65   $159.70  
  7 purchase totals = $1,011.46       $1,094.9562   $1,094.96   $1,095.00   $1,095.00