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 $127.41   11.130%   $141.5907   $141.59   $141.60   $141.60  
  Purchase #2 $234.54   4.469%   $245.0216   $245.02   $245.00   $245.00  
  Purchase #3 $195.70   9.187%   $213.679   $213.68   $213.70   $213.70  
  Purchase #4 $12.58   11.546%   $14.0325   $14.03   $14.05   $14.00  
  Purchase #5 $80.40   5.164%   $84.5519   $84.55   $84.55   $84.60  
  Purchase #6 $214.29   6.151%   $227.471   $227.47   $227.45   $227.50  
  Purchase #7 $227.68   9.444%   $249.1821   $249.18   $249.20   $249.20  
  7 purchase totals = $1,092.60       $1,175.5288   $1,175.52   $1,175.55   $1,175.60