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 $57.33   8.465%   $62.183   $62.18   $62.20   $62.20  
  Purchase #2 $186.56   3.209%   $192.5467   $192.55   $192.55   $192.50  
  Purchase #3 $164.28   9.833%   $180.4337   $180.43   $180.45   $180.40  
  Purchase #4 $197.58   4.709%   $206.884   $206.88   $206.90   $206.90  
  Purchase #5 $83.96   10.364%   $92.6616   $92.66   $92.65   $92.70  
  Purchase #6 $117.31   6.196%   $124.5785   $124.58   $124.60   $124.60  
  Purchase #7 $234.85   3.472%   $243.004   $243.00   $243.00   $243.00  
  7 purchase totals = $1,041.87       $1,102.2915   $1,102.28   $1,102.35   $1,102.30