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 $207.74   8.582%   $225.5682   $225.57   $225.55   $225.60  
  Purchase #2 $143.43   4.493%   $149.8743   $149.87   $149.85   $149.90  
  Purchase #3 $78.77   10.367%   $86.9361   $86.94   $86.95   $86.90  
  Purchase #4 $146.50   7.674%   $157.7424   $157.74   $157.75   $157.70  
  Purchase #5 $113.28   9.308%   $123.8241   $123.82   $123.80   $123.80  
  Purchase #6 $104.57   12.199%   $117.3265   $117.33   $117.35   $117.30  
  Purchase #7 $219.94   6.625%   $234.511   $234.51   $234.50   $234.50  
  7 purchase totals = $1,014.23       $1,095.7826   $1,095.78   $1,095.75   $1,095.70