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 $222.98   4.562%   $233.1523   $233.15   $233.15   $233.20  
  Purchase #2 $231.78   13.279%   $262.5581   $262.56   $262.55   $262.60  
  Purchase #3 $196.42   6.424%   $209.038   $209.04   $209.05   $209.00  
  Purchase #4 $209.29   3.347%   $216.2949   $216.29   $216.30   $216.30  
  Purchase #5 $27.50   9.693%   $30.1656   $30.17   $30.15   $30.20  
  Purchase #6 $102.67   3.853%   $106.6259   $106.63   $106.65   $106.60  
  Purchase #7 $173.65   6.451%   $184.8522   $184.85   $184.85   $184.90  
  7 purchase totals = $1,164.29       $1,242.6870   $1,242.69   $1,242.70   $1,242.80