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 $176.35   4.520%   $184.321   $184.32   $184.30   $184.30  
  Purchase #2 $15.25   7.247%   $16.3552   $16.36   $16.35   $16.40  
  Purchase #3 $25.43   3.546%   $26.3317   $26.33   $26.35   $26.30  
  Purchase #4 $116.90   6.253%   $124.2098   $124.21   $124.20   $124.20  
  Purchase #5 $43.67   4.576%   $45.6683   $45.67   $45.65   $45.70  
  Purchase #6 $47.95   11.537%   $53.482   $53.48   $53.50   $53.50  
  Purchase #7 $9.92   3.155%   $10.233   $10.23   $10.25   $10.20  
  7 purchase totals = $435.47       $460.6010   $460.60   $460.60   $460.60