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 $152.77   5.488%   $161.154   $161.15   $161.15   $161.20  
  Purchase #2 $69.34   5.862%   $73.4047   $73.40   $73.40   $73.40  
  Purchase #3 $210.61   11.713%   $235.2787   $235.28   $235.30   $235.30  
  Purchase #4 $103.65   10.802%   $114.8463   $114.85   $114.85   $114.80  
  Purchase #5 $162.41   7.122%   $173.9768   $173.98   $174.00   $174.00  
  Purchase #6 $212.93   11.623%   $237.6789   $237.68   $237.70   $237.70  
  Purchase #7 $33.31   7.825%   $35.9165   $35.92   $35.90   $35.90  
  7 purchase totals = $945.02       $1,032.2559   $1,032.26   $1,032.30   $1,032.30