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 $182.49   10.772%   $202.1478   $202.15   $202.15   $202.10  
  Purchase #2 $244.86   3.532%   $253.5085   $253.51   $253.50   $253.50  
  Purchase #3 $34.77   7.198%   $37.2727   $37.27   $37.25   $37.30  
  Purchase #4 $213.57   10.264%   $235.4908   $235.49   $235.50   $235.50  
  Purchase #5 $206.99   5.160%   $217.6707   $217.67   $217.65   $217.70  
  Purchase #6 $118.91   7.638%   $127.9923   $127.99   $128.00   $128.00  
  Purchase #7 $250.67   12.690%   $282.48   $282.48   $282.50   $282.50  
  7 purchase totals = $1,252.26       $1,356.5628   $1,356.56   $1,356.55   $1,356.60