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 $63.47   11.363%   $70.6821   $70.68   $70.70   $70.70  
  Purchase #2 $33.86   8.170%   $36.6264   $36.63   $36.65   $36.60  
  Purchase #3 $164.95   3.460%   $170.6573   $170.66   $170.65   $170.70  
  Purchase #4 $250.66   6.743%   $267.562   $267.56   $267.55   $267.60  
  Purchase #5 $236.76   11.776%   $264.6409   $264.64   $264.65   $264.60  
  Purchase #6 $127.79   5.749%   $135.1366   $135.14   $135.15   $135.10  
  Purchase #7 $150.91   11.279%   $167.9311   $167.93   $167.95   $167.90  
  7 purchase totals = $1,028.40       $1,113.2364   $1,113.24   $1,113.30   $1,113.20