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 $159.44   5.249%   $167.809   $167.81   $167.80   $167.80  
  Purchase #2 $230.98   5.227%   $243.0533   $243.05   $243.05   $243.10  
  Purchase #3 $72.49   5.121%   $76.2022   $76.20   $76.20   $76.20  
  Purchase #4 $107.88   11.167%   $119.927   $119.93   $119.95   $119.90  
  Purchase #5 $80.74   8.586%   $87.6723   $87.67   $87.65   $87.70  
  Purchase #6 $102.80   9.784%   $112.858   $112.86   $112.85   $112.90  
  Purchase #7 $239.91   9.321%   $262.272   $262.27   $262.25   $262.30  
  7 purchase totals = $994.24       $1,069.7938   $1,069.79   $1,069.75   $1,069.90