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 $34.96   3.202%   $36.0794   $36.08   $36.10   $36.10  
  Purchase #2 $166.39   9.596%   $182.3568   $182.36   $182.35   $182.40  
  Purchase #3 $188.56   7.674%   $203.0301   $203.03   $203.05   $203.00  
  Purchase #4 $96.46   13.276%   $109.266   $109.27   $109.25   $109.30  
  Purchase #5 $186.78   12.493%   $210.1144   $210.11   $210.10   $210.10  
  Purchase #6 $151.75   11.581%   $169.3242   $169.32   $169.30   $169.30  
  Purchase #7 $157.33   3.801%   $163.3101   $163.31   $163.30   $163.30  
  7 purchase totals = $982.23       $1,073.4810   $1,073.48   $1,073.45   $1,073.50