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 $64.45   7.190%   $69.084   $69.08   $69.10   $69.10  
  Purchase #2 $191.35   5.332%   $201.5528   $201.55   $201.55   $201.60  
  Purchase #3 $117.36   11.112%   $130.401   $130.40   $130.40   $130.40  
  Purchase #4 $165.78   11.218%   $184.3772   $184.38   $184.40   $184.40  
  Purchase #5 $34.59   11.833%   $38.683   $38.68   $38.70   $38.70  
  Purchase #6 $176.76   7.783%   $190.5172   $190.52   $190.50   $190.50  
  Purchase #7 $130.37   6.112%   $138.3382   $138.34   $138.35   $138.30  
  7 purchase totals = $880.66       $952.9534   $952.95   $953.00   $953.00