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 $182.63   6.512%   $194.5229   $194.52   $194.50   $194.50  
  Purchase #2 $156.64   5.806%   $165.7345   $165.73   $165.75   $165.70  
  Purchase #3 $67.86   12.283%   $76.1952   $76.20   $76.20   $76.20  
  Purchase #4 $249.49   7.852%   $269.08   $269.08   $269.10   $269.10  
  Purchase #5 $146.92   5.466%   $154.9506   $154.95   $154.95   $155.00  
  Purchase #6 $117.89   5.380%   $124.2325   $124.23   $124.25   $124.20  
  Purchase #7 $62.42   5.699%   $65.9773   $65.98   $66.00   $66.00  
  7 purchase totals = $983.85       $1,050.6930   $1,050.69   $1,050.75   $1,050.70