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 $169.46   7.390%   $181.9831   $181.98   $182.00   $182.00  
  Purchase #2 $238.81   4.842%   $250.3732   $250.37   $250.35   $250.40  
  Purchase #3 $117.56   5.863%   $124.4525   $124.45   $124.45   $124.50  
  Purchase #4 $248.41   6.339%   $264.1567   $264.16   $264.15   $264.20  
  Purchase #5 $63.67   12.102%   $71.3753   $71.38   $71.40   $71.40  
  Purchase #6 $76.64   5.835%   $81.1119   $81.11   $81.10   $81.10  
  Purchase #7 $104.71   13.827%   $119.1883   $119.19   $119.20   $119.20  
  7 purchase totals = $1,019.26       $1,092.6410   $1,092.64   $1,092.65   $1,092.80