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 $41.69   10.362%   $46.0099   $46.01   $46.00   $46.00  
  Purchase #2 $32.82   11.625%   $36.6353   $36.64   $36.65   $36.60  
  Purchase #3 $224.68   13.728%   $255.5241   $255.52   $255.50   $255.50  
  Purchase #4 $80.48   6.469%   $85.6863   $85.69   $85.70   $85.70  
  Purchase #5 $223.71   5.434%   $235.8664   $235.87   $235.85   $235.90  
  Purchase #6 $139.44   5.771%   $147.4871   $147.49   $147.50   $147.50  
  Purchase #7 $207.83   10.737%   $230.1447   $230.14   $230.15   $230.10  
  7 purchase totals = $950.65       $1,037.3538   $1,037.36   $1,037.35   $1,037.30