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 $111.43   3.310%   $115.1183   $115.12   $115.10   $115.10  
  Purchase #2 $57.48   13.431%   $65.2001   $65.20   $65.20   $65.20  
  Purchase #3 $57.39   8.752%   $62.4128   $62.41   $62.40   $62.40  
  Purchase #4 $80.25   7.644%   $86.3843   $86.38   $86.40   $86.40  
  Purchase #5 $164.61   5.648%   $173.9072   $173.91   $173.90   $173.90  
  Purchase #6 $209.45   5.147%   $220.2304   $220.23   $220.25   $220.20  
  Purchase #7 $196.68   3.119%   $202.8144   $202.81   $202.80   $202.80  
  7 purchase totals = $877.29       $926.0675   $926.06   $926.05   $926.00