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 $72.30   7.218%   $77.5186   $77.52   $77.50   $77.50  
  Purchase #2 $205.48   7.371%   $220.6259   $220.63   $220.65   $220.60  
  Purchase #3 $32.77   7.395%   $35.1933   $35.19   $35.20   $35.20  
  Purchase #4 $100.88   8.619%   $109.5748   $109.57   $109.55   $109.60  
  Purchase #5 $217.93   12.602%   $245.3935   $245.39   $245.40   $245.40  
  Purchase #6 $229.83   8.298%   $248.9013   $248.90   $248.90   $248.90  
  Purchase #7 $103.41   6.698%   $110.3364   $110.34   $110.35   $110.30  
  7 purchase totals = $962.60       $1,047.5438   $1,047.54   $1,047.55   $1,047.50