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 $91.66   4.147%   $95.4611   $95.46   $95.45   $95.50  
  Purchase #2 $113.93   13.405%   $129.2023   $129.20   $129.20   $129.20  
  Purchase #3 $56.48   9.110%   $61.6253   $61.63   $61.65   $61.60  
  Purchase #4 $209.91   6.209%   $222.9433   $222.94   $222.95   $222.90  
  Purchase #5 $114.38   11.693%   $127.7545   $127.75   $127.75   $127.80  
  Purchase #6 $231.35   8.561%   $251.1559   $251.16   $251.15   $251.20  
  Purchase #7 $136.41   9.844%   $149.8382   $149.84   $149.85   $149.80  
  7 purchase totals = $954.12       $1,037.9806   $1,037.98   $1,038.00   $1,038.00