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 $124.48   13.787%   $141.6421   $141.64   $141.65   $141.60  
  Purchase #2 $155.55   9.518%   $170.3552   $170.36   $170.35   $170.40  
  Purchase #3 $144.78   11.123%   $160.8839   $160.88   $160.90   $160.90  
  Purchase #4 $169.81   5.662%   $179.4246   $179.42   $179.40   $179.40  
  Purchase #5 $104.32   8.528%   $113.2164   $113.22   $113.20   $113.20  
  Purchase #6 $174.39   10.463%   $192.6364   $192.64   $192.65   $192.60  
  Purchase #7 $140.80   4.106%   $146.5812   $146.58   $146.60   $146.60  
  7 purchase totals = $1,014.13       $1,104.7398   $1,104.74   $1,104.75   $1,104.70