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 $59.62   3.640%   $61.7902   $61.79   $61.80   $61.80  
  Purchase #2 $154.76   8.703%   $168.2288   $168.23   $168.25   $168.20  
  Purchase #3 $89.69   4.161%   $93.422   $93.42   $93.40   $93.40  
  Purchase #4 $118.90   4.332%   $124.0507   $124.05   $124.05   $124.10  
  Purchase #5 $150.89   4.205%   $157.2349   $157.23   $157.25   $157.20  
  Purchase #6 $91.50   5.390%   $96.4319   $96.43   $96.45   $96.40  
  Purchase #7 $23.34   4.426%   $24.373   $24.37   $24.35   $24.40  
  7 purchase totals = $688.70       $725.5315   $725.52   $725.55   $725.50