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 $108.81   5.303%   $114.5802   $114.58   $114.60   $114.60  
  Purchase #2 $195.65   3.167%   $201.8462   $201.85   $201.85   $201.80  
  Purchase #3 $127.26   9.494%   $139.3421   $139.34   $139.35   $139.30  
  Purchase #4 $235.66   13.842%   $268.2801   $268.28   $268.30   $268.30  
  Purchase #5 $165.87   5.604%   $175.1654   $175.17   $175.15   $175.20  
  Purchase #6 $185.48   10.472%   $204.9035   $204.90   $204.90   $204.90  
  Purchase #7 $235.25   12.317%   $264.2257   $264.23   $264.25   $264.20  
  7 purchase totals = $1,253.98       $1,368.3432   $1,368.35   $1,368.40   $1,368.30