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 $184.41   5.842%   $195.1832   $195.18   $195.20   $195.20  
  Purchase #2 $24.64   9.143%   $26.8928   $26.89   $26.90   $26.90  
  Purchase #3 $199.87   4.531%   $208.9261   $208.93   $208.95   $208.90  
  Purchase #4 $72.88   4.832%   $76.4016   $76.40   $76.40   $76.40  
  Purchase #5 $158.82   8.839%   $172.8581   $172.86   $172.85   $172.90  
  Purchase #6 $79.43   10.488%   $87.7606   $87.76   $87.75   $87.80  
  Purchase #7 $212.94   8.277%   $230.565   $230.57   $230.55   $230.60  
  7 purchase totals = $932.99       $998.5874   $998.59   $998.60   $998.70