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 $176.37   11.721%   $197.0423   $197.04   $197.05   $197.00  
  Purchase #2 $183.31   12.375%   $205.9946   $205.99   $206.00   $206.00  
  Purchase #3 $38.36   11.833%   $42.8991   $42.90   $42.90   $42.90  
  Purchase #4 $146.60   8.511%   $159.0771   $159.08   $159.10   $159.10  
  Purchase #5 $209.78   5.611%   $221.5508   $221.55   $221.55   $221.60  
  Purchase #6 $107.76   12.705%   $121.4509   $121.45   $121.45   $121.50  
  Purchase #7 $214.40   11.375%   $238.788   $238.79   $238.80   $238.80  
  7 purchase totals = $1,076.58       $1,186.8028   $1,186.80   $1,186.85   $1,186.90