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 $59.90   4.470%   $62.5775   $62.58   $62.60   $62.60  
  Purchase #2 $119.86   11.437%   $133.5684   $133.57   $133.55   $133.60  
  Purchase #3 $210.77   3.493%   $218.1322   $218.13   $218.15   $218.10  
  Purchase #4 $208.96   11.402%   $232.7856   $232.79   $232.80   $232.80  
  Purchase #5 $190.44   11.679%   $212.6815   $212.68   $212.70   $212.70  
  Purchase #6 $103.38   13.377%   $117.2091   $117.21   $117.20   $117.20  
  Purchase #7 $172.39   12.728%   $194.3318   $194.33   $194.35   $194.30  
  7 purchase totals = $1,065.70       $1,171.2861   $1,171.29   $1,171.35   $1,171.30