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 $13.83   4.559%   $14.4605   $14.46   $14.45   $14.50  
  Purchase #2 $115.48   9.810%   $126.8086   $126.81   $126.80   $126.80  
  Purchase #3 $203.51   3.144%   $209.9084   $209.91   $209.90   $209.90  
  Purchase #4 $235.30   4.227%   $245.2461   $245.25   $245.25   $245.20  
  Purchase #5 $193.79   6.522%   $206.429   $206.43   $206.45   $206.40  
  Purchase #6 $200.96   6.637%   $214.2977   $214.30   $214.30   $214.30  
  Purchase #7 $57.56   4.624%   $60.2216   $60.22   $60.20   $60.20  
  7 purchase totals = $1,020.43       $1,077.3719   $1,077.38   $1,077.35   $1,077.30