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 $65.62   5.419%   $69.1759   $69.18   $69.20   $69.20  
  Purchase #2 $132.91   13.140%   $150.3744   $150.37   $150.35   $150.40  
  Purchase #3 $178.83   6.217%   $189.9479   $189.95   $189.95   $189.90  
  Purchase #4 $238.89   9.546%   $261.6944   $261.69   $261.70   $261.70  
  Purchase #5 $214.78   8.651%   $233.3606   $233.36   $233.35   $233.40  
  Purchase #6 $210.46   9.398%   $230.239   $230.24   $230.25   $230.20  
  Purchase #7 $11.59   11.807%   $12.9584   $12.96   $12.95   $13.00  
  7 purchase totals = $1,053.08       $1,147.7506   $1,147.75   $1,147.75   $1,147.80