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 $104.68   4.691%   $109.5905   $109.59   $109.60   $109.60  
  Purchase #2 $168.87   3.232%   $174.3279   $174.33   $174.35   $174.30  
  Purchase #3 $105.93   10.584%   $117.1416   $117.14   $117.15   $117.10  
  Purchase #4 $238.64   8.614%   $259.1964   $259.20   $259.20   $259.20  
  Purchase #5 $136.43   11.208%   $151.7211   $151.72   $151.70   $151.70  
  Purchase #6 $233.53   5.413%   $246.171   $246.17   $246.15   $246.20  
  Purchase #7 $58.94   13.371%   $66.8209   $66.82   $66.80   $66.80  
  7 purchase totals = $1,047.02       $1,124.9694   $1,124.97   $1,124.95   $1,124.90