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 $52.53   11.590%   $58.6182   $58.62   $58.60   $58.60  
  Purchase #2 $224.29   10.163%   $247.0846   $247.08   $247.10   $247.10  
  Purchase #3 $72.42   10.630%   $80.1182   $80.12   $80.10   $80.10  
  Purchase #4 $67.37   13.582%   $76.5202   $76.52   $76.50   $76.50  
  Purchase #5 $169.36   4.795%   $177.4808   $177.48   $177.50   $177.50  
  Purchase #6 $136.75   6.373%   $145.4651   $145.47   $145.45   $145.50  
  Purchase #7 $232.67   12.170%   $260.9859   $260.99   $261.00   $261.00  
  7 purchase totals = $955.39       $1,046.2730   $1,046.28   $1,046.25   $1,046.30