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 $244.66   7.756%   $263.6358   $263.64   $263.65   $263.60  
  Purchase #2 $191.47   12.287%   $214.9959   $215.00   $215.00   $215.00  
  Purchase #3 $77.49   4.213%   $80.7547   $80.75   $80.75   $80.80  
  Purchase #4 $164.52   11.871%   $184.0502   $184.05   $184.05   $184.10  
  Purchase #5 $119.35   11.486%   $133.0585   $133.06   $133.05   $133.10  
  Purchase #6 $233.73   12.626%   $263.2407   $263.24   $263.25   $263.20  
  Purchase #7 $54.43   3.245%   $56.1963   $56.20   $56.20   $56.20  
  7 purchase totals = $1,085.65       $1,195.9321   $1,195.94   $1,195.95   $1,196.00