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 $214.76   9.684%   $235.5574   $235.56   $235.55   $235.60  
  Purchase #2 $231.93   8.651%   $251.9943   $251.99   $252.00   $252.00  
  Purchase #3 $94.98   7.211%   $101.829   $101.83   $101.85   $101.80  
  Purchase #4 $245.65   12.625%   $276.6633   $276.66   $276.65   $276.70  
  Purchase #5 $83.90   4.778%   $87.9087   $87.91   $87.90   $87.90  
  Purchase #6 $123.61   11.573%   $137.9154   $137.92   $137.90   $137.90  
  Purchase #7 $126.39   5.840%   $133.7712   $133.77   $133.75   $133.80  
  7 purchase totals = $1,121.22       $1,225.6393   $1,225.64   $1,225.60   $1,225.70