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 $144.59   5.574%   $152.6494   $152.65   $152.65   $152.60  
  Purchase #2 $184.26   13.838%   $209.7579   $209.76   $209.75   $209.80  
  Purchase #3 $31.45   11.164%   $34.9611   $34.96   $34.95   $35.00  
  Purchase #4 $58.45   9.112%   $63.776   $63.78   $63.80   $63.80  
  Purchase #5 $222.46   5.200%   $234.0279   $234.03   $234.05   $234.00  
  Purchase #6 $219.47   10.214%   $241.8867   $241.89   $241.90   $241.90  
  Purchase #7 $242.35   11.821%   $270.9982   $271.00   $271.00   $271.00  
  7 purchase totals = $1,103.03       $1,208.0572   $1,208.07   $1,208.10   $1,208.10