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 $67.35   5.587%   $71.1128   $71.11   $71.10   $71.10  
  Purchase #2 $135.32   9.852%   $148.6517   $148.65   $148.65   $148.70  
  Purchase #3 $50.29   7.699%   $54.1618   $54.16   $54.15   $54.20  
  Purchase #4 $57.50   6.246%   $61.0915   $61.09   $61.10   $61.10  
  Purchase #5 $82.88   3.845%   $86.0667   $86.07   $86.05   $86.10  
  Purchase #6 $213.99   6.579%   $228.0684   $228.07   $228.05   $228.10  
  Purchase #7 $79.74   7.584%   $85.7875   $85.79   $85.80   $85.80  
  7 purchase totals = $687.07       $734.9404   $734.94   $734.90   $735.10