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 $56.92   9.486%   $62.3194   $62.32   $62.30   $62.30  
  Purchase #2 $213.69   8.470%   $231.7895   $231.79   $231.80   $231.80  
  Purchase #3 $232.64   7.794%   $250.772   $250.77   $250.75   $250.80  
  Purchase #4 $36.58   6.743%   $39.0466   $39.05   $39.05   $39.00  
  Purchase #5 $243.41   7.566%   $261.8264   $261.83   $261.85   $261.80  
  Purchase #6 $123.63   3.251%   $127.6492   $127.65   $127.65   $127.60  
  Purchase #7 $104.72   13.655%   $119.0195   $119.02   $119.00   $119.00  
  7 purchase totals = $1,011.59       $1,092.4226   $1,092.43   $1,092.40   $1,092.30