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 $92.49   3.442%   $95.6735   $95.67   $95.65   $95.70  
  Purchase #2 $114.59   8.147%   $123.9256   $123.93   $123.95   $123.90  
  Purchase #3 $209.31   7.511%   $225.0313   $225.03   $225.05   $225.00  
  Purchase #4 $25.96   5.513%   $27.3912   $27.39   $27.40   $27.40  
  Purchase #5 $210.85   9.716%   $231.3362   $231.34   $231.35   $231.30  
  Purchase #6 $102.79   10.677%   $113.7649   $113.76   $113.75   $113.80  
  Purchase #7 $250.40   10.367%   $276.359   $276.36   $276.35   $276.40  
  7 purchase totals = $1,006.39       $1,093.4817   $1,093.48   $1,093.50   $1,093.50