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 $215.92   8.247%   $233.7269   $233.73   $233.75   $233.70  
  Purchase #2 $197.81   10.565%   $218.7086   $218.71   $218.70   $218.70  
  Purchase #3 $21.52   12.651%   $24.2425   $24.24   $24.25   $24.20  
  Purchase #4 $210.75   8.194%   $228.0189   $228.02   $228.00   $228.00  
  Purchase #5 $230.28   6.387%   $244.988   $244.99   $245.00   $245.00  
  Purchase #6 $151.93   4.159%   $158.2488   $158.25   $158.25   $158.20  
  Purchase #7 $17.89   6.857%   $19.1167   $19.12   $19.10   $19.10  
  7 purchase totals = $1,046.10       $1,127.0504   $1,127.06   $1,127.05   $1,126.90