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 $216.65   13.140%   $245.1178   $245.12   $245.10   $245.10  
  Purchase #2 $209.31   8.784%   $227.6958   $227.70   $227.70   $227.70  
  Purchase #3 $158.69   10.229%   $174.9224   $174.92   $174.90   $174.90  
  Purchase #4 $49.83   12.644%   $56.1305   $56.13   $56.15   $56.10  
  Purchase #5 $156.64   12.224%   $175.7877   $175.79   $175.80   $175.80  
  Purchase #6 $91.49   10.617%   $101.2035   $101.20   $101.20   $101.20  
  Purchase #7 $141.63   3.506%   $146.5955   $146.60   $146.60   $146.60  
  7 purchase totals = $1,024.24       $1,127.4532   $1,127.46   $1,127.45   $1,127.40