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 $86.73   10.393%   $95.7438   $95.74   $95.75   $95.70  
  Purchase #2 $116.41   3.696%   $120.7125   $120.71   $120.70   $120.70  
  Purchase #3 $70.82   5.147%   $74.4651   $74.47   $74.45   $74.50  
  Purchase #4 $225.80   12.449%   $253.9098   $253.91   $253.90   $253.90  
  Purchase #5 $57.80   12.736%   $65.1614   $65.16   $65.15   $65.20  
  Purchase #6 $165.60   4.566%   $173.1613   $173.16   $173.15   $173.20  
  Purchase #7 $224.38   11.832%   $250.9286   $250.93   $250.95   $250.90  
  7 purchase totals = $947.54       $1,034.0825   $1,034.08   $1,034.05   $1,034.10