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 $239.82   9.516%   $262.6413   $262.64   $262.65   $262.60  
  Purchase #2 $168.98   9.350%   $184.7796   $184.78   $184.80   $184.80  
  Purchase #3 $21.71   13.570%   $24.656   $24.66   $24.65   $24.70  
  Purchase #4 $158.33   13.803%   $180.1843   $180.18   $180.20   $180.20  
  Purchase #5 $136.69   13.772%   $155.5149   $155.51   $155.50   $155.50  
  Purchase #6 $41.80   13.497%   $47.4417   $47.44   $47.45   $47.40  
  Purchase #7 $206.48   3.142%   $212.9676   $212.97   $212.95   $213.00  
  7 purchase totals = $973.81       $1,068.1854   $1,068.18   $1,068.20   $1,068.20