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 $57.53   7.709%   $61.965   $61.97   $61.95   $62.00  
  Purchase #2 $244.68   8.621%   $265.7739   $265.77   $265.75   $265.80  
  Purchase #3 $169.62   9.282%   $185.3641   $185.36   $185.35   $185.40  
  Purchase #4 $155.25   13.499%   $176.2072   $176.21   $176.20   $176.20  
  Purchase #5 $241.90   6.635%   $257.9501   $257.95   $257.95   $258.00  
  Purchase #6 $143.77   4.488%   $150.2224   $150.22   $150.20   $150.20  
  Purchase #7 $237.60   6.169%   $252.2575   $252.26   $252.25   $252.30  
  7 purchase totals = $1,250.35       $1,349.7402   $1,349.74   $1,349.65   $1,349.90