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 $67.52   8.786%   $73.4523   $73.45   $73.45   $73.50  
  Purchase #2 $238.60   12.413%   $268.2174   $268.22   $268.20   $268.20  
  Purchase #3 $234.71   7.438%   $252.1677   $252.17   $252.15   $252.20  
  Purchase #4 $112.33   12.564%   $126.4431   $126.44   $126.45   $126.40  
  Purchase #5 $215.64   7.421%   $231.6426   $231.64   $231.65   $231.60  
  Purchase #6 $203.38   6.769%   $217.1468   $217.15   $217.15   $217.10  
  Purchase #7 $64.77   6.345%   $68.8797   $68.88   $68.90   $68.90  
  7 purchase totals = $1,136.95       $1,237.9496   $1,237.95   $1,237.95   $1,237.90