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 $233.33   8.848%   $253.975   $253.98   $254.00   $254.00  
  Purchase #2 $64.74   8.151%   $70.017   $70.02   $70.00   $70.00  
  Purchase #3 $157.54   6.803%   $168.2574   $168.26   $168.25   $168.30  
  Purchase #4 $193.88   3.408%   $200.4874   $200.49   $200.50   $200.50  
  Purchase #5 $129.56   9.137%   $141.3979   $141.40   $141.40   $141.40  
  Purchase #6 $62.97   10.678%   $69.6939   $69.69   $69.70   $69.70  
  Purchase #7 $179.84   9.673%   $197.2359   $197.24   $197.25   $197.20  
  7 purchase totals = $1,021.86       $1,101.0645   $1,101.08   $1,101.10   $1,101.10