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 $82.90   13.160%   $93.8096   $93.81   $93.80   $93.80  
  Purchase #2 $188.94   10.341%   $208.4783   $208.48   $208.50   $208.50  
  Purchase #3 $245.47   9.835%   $269.612   $269.61   $269.60   $269.60  
  Purchase #4 $131.29   7.437%   $141.054   $141.05   $141.05   $141.10  
  Purchase #5 $223.26   6.711%   $238.243   $238.24   $238.25   $238.20  
  Purchase #6 $145.87   10.375%   $161.004   $161.00   $161.00   $161.00  
  Purchase #7 $187.62   13.714%   $213.3502   $213.35   $213.35   $213.40  
  7 purchase totals = $1,205.35       $1,325.5511   $1,325.54   $1,325.55   $1,325.60