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 $172.94   13.148%   $195.6782   $195.68   $195.70   $195.70  
  Purchase #2 $21.54   12.187%   $24.1651   $24.17   $24.15   $24.20  
  Purchase #3 $51.63   10.739%   $57.1745   $57.17   $57.15   $57.20  
  Purchase #4 $151.62   5.573%   $160.0698   $160.07   $160.05   $160.10  
  Purchase #5 $60.45   4.796%   $63.3492   $63.35   $63.35   $63.30  
  Purchase #6 $187.84   3.145%   $193.7476   $193.75   $193.75   $193.70  
  Purchase #7 $187.84   5.323%   $197.8387   $197.84   $197.85   $197.80  
  7 purchase totals = $833.86       $892.0231   $892.03   $892.00   $892.00