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 $195.67   5.803%   $207.0247   $207.02   $207.00   $207.00  
  Purchase #2 $24.59   7.227%   $26.3671   $26.37   $26.35   $26.40  
  Purchase #3 $76.30   12.866%   $86.1168   $86.12   $86.10   $86.10  
  Purchase #4 $187.51   13.419%   $212.672   $212.67   $212.65   $212.70  
  Purchase #5 $87.74   6.374%   $93.3325   $93.33   $93.35   $93.30  
  Purchase #6 $162.66   6.429%   $173.1174   $173.12   $173.10   $173.10  
  Purchase #7 $107.97   10.256%   $119.0434   $119.04   $119.05   $119.00  
  7 purchase totals = $842.44       $917.6739   $917.67   $917.60   $917.60