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 $124.95   7.209%   $133.9576   $133.96   $133.95   $134.00  
  Purchase #2 $203.78   3.862%   $211.65   $211.65   $211.65   $211.70  
  Purchase #3 $191.86   5.191%   $201.8195   $201.82   $201.80   $201.80  
  Purchase #4 $239.36   6.809%   $255.658   $255.66   $255.65   $255.70  
  Purchase #5 $12.68   10.453%   $14.0054   $14.01   $14.00   $14.00  
  Purchase #6 $15.76   9.124%   $17.1979   $17.20   $17.20   $17.20  
  Purchase #7 $249.70   8.374%   $270.6099   $270.61   $270.60   $270.60  
  7 purchase totals = $1,038.09       $1,104.8983   $1,104.91   $1,104.85   $1,105.00