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 $178.38   9.620%   $195.5402   $195.54   $195.55   $195.50  
  Purchase #2 $183.52   7.174%   $196.6857   $196.69   $196.70   $196.70  
  Purchase #3 $240.66   9.364%   $263.1954   $263.20   $263.20   $263.20  
  Purchase #4 $61.64   4.597%   $64.4736   $64.47   $64.45   $64.50  
  Purchase #5 $205.34   3.824%   $213.1922   $213.19   $213.20   $213.20  
  Purchase #6 $97.54   13.645%   $110.8493   $110.85   $110.85   $110.80  
  Purchase #7 $204.98   5.795%   $216.8586   $216.86   $216.85   $216.90  
  7 purchase totals = $1,172.06       $1,260.7950   $1,260.80   $1,260.80   $1,260.80