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 $205.53   8.483%   $222.9651   $222.97   $222.95   $223.00  
  Purchase #2 $208.50   7.352%   $223.8289   $223.83   $223.85   $223.80  
  Purchase #3 $142.95   12.656%   $161.0418   $161.04   $161.05   $161.00  
  Purchase #4 $191.69   6.607%   $204.355   $204.36   $204.35   $204.40  
  Purchase #5 $229.30   13.636%   $260.5673   $260.57   $260.55   $260.60  
  Purchase #6 $141.57   4.763%   $148.313   $148.31   $148.30   $148.30  
  Purchase #7 $232.88   3.554%   $241.1566   $241.16   $241.15   $241.20  
  7 purchase totals = $1,352.42       $1,462.2277   $1,462.24   $1,462.20   $1,462.30