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 $174.25   11.108%   $193.6057   $193.61   $193.60   $193.60  
  Purchase #2 $168.80   5.363%   $177.8527   $177.85   $177.85   $177.90  
  Purchase #3 $148.62   12.466%   $167.147   $167.15   $167.15   $167.10  
  Purchase #4 $160.43   8.351%   $173.8275   $173.83   $173.85   $173.80  
  Purchase #5 $199.51   13.629%   $226.7012   $226.70   $226.70   $226.70  
  Purchase #6 $205.50   4.253%   $214.2399   $214.24   $214.25   $214.20  
  Purchase #7 $205.46   13.515%   $233.2279   $233.23   $233.25   $233.20  
  7 purchase totals = $1,262.57       $1,386.6019   $1,386.61   $1,386.65   $1,386.50