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 $230.29   6.723%   $245.7724   $245.77   $245.75   $245.80  
  Purchase #2 $192.65   7.562%   $207.2182   $207.22   $207.20   $207.20  
  Purchase #3 $59.63   8.391%   $64.6336   $64.63   $64.65   $64.60  
  Purchase #4 $173.38   12.353%   $194.7976   $194.80   $194.80   $194.80  
  Purchase #5 $147.26   6.121%   $156.2738   $156.27   $156.25   $156.30  
  Purchase #6 $69.48   4.240%   $72.426   $72.43   $72.45   $72.40  
  Purchase #7 $62.56   11.342%   $69.6556   $69.66   $69.65   $69.70  
  7 purchase totals = $935.25       $1,010.7772   $1,010.78   $1,010.75   $1,010.80