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 $110.30   7.427%   $118.492   $118.49   $118.50   $118.50  
  Purchase #2 $147.48   3.520%   $152.6713   $152.67   $152.65   $152.70  
  Purchase #3 $226.39   12.632%   $254.9876   $254.99   $255.00   $255.00  
  Purchase #4 $245.61   8.778%   $267.1696   $267.17   $267.15   $267.20  
  Purchase #5 $203.65   6.586%   $217.0624   $217.06   $217.05   $217.10  
  Purchase #6 $57.42   9.181%   $62.6917   $62.69   $62.70   $62.70  
  Purchase #7 $73.96   3.845%   $76.8038   $76.80   $76.80   $76.80  
  7 purchase totals = $1,064.81       $1,149.8784   $1,149.87   $1,149.85   $1,150.00