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 $82.48   12.383%   $92.6935   $92.69   $92.70   $92.70  
  Purchase #2 $108.26   10.432%   $119.5537   $119.55   $119.55   $119.60  
  Purchase #3 $162.62   12.367%   $182.7312   $182.73   $182.75   $182.70  
  Purchase #4 $211.43   5.278%   $222.5893   $222.59   $222.60   $222.60  
  Purchase #5 $184.29   9.576%   $201.9376   $201.94   $201.95   $201.90  
  Purchase #6 $22.33   3.700%   $23.1562   $23.16   $23.15   $23.20  
  Purchase #7 $182.25   5.715%   $192.6656   $192.67   $192.65   $192.70  
  7 purchase totals = $953.66       $1,035.3271   $1,035.33   $1,035.35   $1,035.40