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 $110.48   13.764%   $125.6865   $125.69   $125.70   $125.70  
  Purchase #2 $225.59   10.223%   $248.6521   $248.65   $248.65   $248.70  
  Purchase #3 $237.94   3.204%   $245.5636   $245.56   $245.55   $245.60  
  Purchase #4 $170.47   11.562%   $190.1797   $190.18   $190.20   $190.20  
  Purchase #5 $52.25   4.225%   $54.4576   $54.46   $54.45   $54.50  
  Purchase #6 $192.38   9.304%   $210.279   $210.28   $210.30   $210.30  
  Purchase #7 $82.73   10.308%   $91.2578   $91.26   $91.25   $91.30  
  7 purchase totals = $1,071.84       $1,166.0763   $1,166.08   $1,166.10   $1,166.30