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 $121.82   3.169%   $125.6805   $125.68   $125.70   $125.70  
  Purchase #2 $158.84   10.339%   $175.2625   $175.26   $175.25   $175.30  
  Purchase #3 $88.25   9.273%   $96.4334   $96.43   $96.45   $96.40  
  Purchase #4 $237.88   12.772%   $268.262   $268.26   $268.25   $268.30  
  Purchase #5 $91.76   7.665%   $98.7934   $98.79   $98.80   $98.80  
  Purchase #6 $178.60   9.570%   $195.692   $195.69   $195.70   $195.70  
  Purchase #7 $91.45   13.526%   $103.8195   $103.82   $103.80   $103.80  
  7 purchase totals = $968.60       $1,063.9433   $1,063.93   $1,063.95   $1,064.00