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 $95.26   3.220%   $98.3274   $98.33   $98.35   $98.30  
  Purchase #2 $155.31   3.496%   $160.7396   $160.74   $160.75   $160.70  
  Purchase #3 $201.82   11.429%   $224.886   $224.89   $224.90   $224.90  
  Purchase #4 $182.25   6.541%   $194.171   $194.17   $194.15   $194.20  
  Purchase #5 $151.69   13.682%   $172.4442   $172.44   $172.45   $172.40  
  Purchase #6 $180.97   13.479%   $205.3629   $205.36   $205.35   $205.40  
  Purchase #7 $192.81   4.378%   $201.2512   $201.25   $201.25   $201.30  
  7 purchase totals = $1,160.11       $1,257.1823   $1,257.18   $1,257.20   $1,257.20