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 $163.69   11.332%   $182.2394   $182.24   $182.25   $182.20  
  Purchase #2 $212.83   9.457%   $232.9573   $232.96   $232.95   $233.00  
  Purchase #3 $5.96   5.716%   $6.3007   $6.30   $6.30   $6.30  
  Purchase #4 $13.28   7.249%   $14.2427   $14.24   $14.25   $14.20  
  Purchase #5 $186.84   5.229%   $196.6099   $196.61   $196.60   $196.60  
  Purchase #6 $214.82   10.604%   $237.5995   $237.60   $237.60   $237.60  
  Purchase #7 $249.79   3.695%   $259.0197   $259.02   $259.00   $259.00  
  7 purchase totals = $1,047.21       $1,128.9692   $1,128.97   $1,128.95   $1,128.90