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 $192.81   11.308%   $214.613   $214.61   $214.60   $214.60  
  Purchase #2 $175.51   12.579%   $197.5874   $197.59   $197.60   $197.60  
  Purchase #3 $13.60   7.670%   $14.6431   $14.64   $14.65   $14.60  
  Purchase #4 $207.53   5.791%   $219.5481   $219.55   $219.55   $219.50  
  Purchase #5 $79.37   9.264%   $86.7228   $86.72   $86.70   $86.70  
  Purchase #6 $95.34   12.521%   $107.2775   $107.28   $107.30   $107.30  
  Purchase #7 $235.29   8.410%   $255.0779   $255.08   $255.10   $255.10  
  7 purchase totals = $999.45       $1,095.4698   $1,095.47   $1,095.50   $1,095.40