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 $67.53   5.220%   $71.0551   $71.06   $71.05   $71.10  
  Purchase #2 $169.79   11.343%   $189.0493   $189.05   $189.05   $189.00  
  Purchase #3 $90.26   4.851%   $94.6385   $94.64   $94.65   $94.60  
  Purchase #4 $174.44   7.110%   $186.8427   $186.84   $186.85   $186.80  
  Purchase #5 $210.25   3.754%   $218.1428   $218.14   $218.15   $218.10  
  Purchase #6 $243.29   13.496%   $276.1244   $276.12   $276.10   $276.10  
  Purchase #7 $67.67   6.389%   $71.9934   $71.99   $72.00   $72.00  
  7 purchase totals = $1,023.23       $1,107.8462   $1,107.84   $1,107.85   $1,107.70