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 $61.34   3.441%   $63.4507   $63.45   $63.45   $63.50  
  Purchase #2 $159.78   6.153%   $169.6113   $169.61   $169.60   $169.60  
  Purchase #3 $188.79   6.294%   $200.6724   $200.67   $200.65   $200.70  
  Purchase #4 $150.72   10.177%   $166.0588   $166.06   $166.05   $166.10  
  Purchase #5 $214.35   7.200%   $229.7832   $229.78   $229.80   $229.80  
  Purchase #6 $196.33   7.640%   $211.3296   $211.33   $211.35   $211.30  
  Purchase #7 $150.41   7.869%   $162.2458   $162.25   $162.25   $162.20  
  7 purchase totals = $1,121.72       $1,203.1518   $1,203.15   $1,203.15   $1,203.20