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 $218.93   6.692%   $233.5808   $233.58   $233.60   $233.60  
  Purchase #2 $126.30   12.225%   $141.7402   $141.74   $141.75   $141.70  
  Purchase #3 $145.34   7.452%   $156.1707   $156.17   $156.15   $156.20  
  Purchase #4 $225.29   3.357%   $232.853   $232.85   $232.85   $232.90  
  Purchase #5 $113.54   6.241%   $120.626   $120.63   $120.65   $120.60  
  Purchase #6 $43.26   10.405%   $47.7612   $47.76   $47.75   $47.80  
  Purchase #7 $244.68   8.269%   $264.9126   $264.91   $264.90   $264.90  
  7 purchase totals = $1,117.34       $1,197.6445   $1,197.64   $1,197.65   $1,197.70