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 $68.59   12.499%   $77.1631   $77.16   $77.15   $77.20  
  Purchase #2 $160.48   6.366%   $170.6962   $170.70   $170.70   $170.70  
  Purchase #3 $215.97   8.342%   $233.9862   $233.99   $234.00   $234.00  
  Purchase #4 $174.44   5.177%   $183.4708   $183.47   $183.45   $183.50  
  Purchase #5 $62.44   11.238%   $69.457   $69.46   $69.45   $69.50  
  Purchase #6 $201.87   5.111%   $212.1876   $212.19   $212.20   $212.20  
  Purchase #7 $170.29   4.416%   $177.81   $177.81   $177.80   $177.80  
  7 purchase totals = $1,054.08       $1,124.7709   $1,124.78   $1,124.75   $1,124.90