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 $174.55   13.232%   $197.6465   $197.65   $197.65   $197.60  
  Purchase #2 $185.56   4.187%   $193.3294   $193.33   $193.35   $193.30  
  Purchase #3 $60.52   9.501%   $66.27   $66.27   $66.25   $66.30  
  Purchase #4 $163.85   12.716%   $184.6852   $184.69   $184.70   $184.70  
  Purchase #5 $105.55   7.869%   $113.8557   $113.86   $113.85   $113.90  
  Purchase #6 $218.75   9.644%   $239.8463   $239.85   $239.85   $239.80  
  Purchase #7 $164.79   11.424%   $183.6156   $183.62   $183.60   $183.60  
  7 purchase totals = $1,073.57       $1,179.2487   $1,179.27   $1,179.25   $1,179.20