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 $103.88   7.524%   $111.6959   $111.70   $111.70   $111.70  
  Purchase #2 $211.27   11.305%   $235.1541   $235.15   $235.15   $235.20  
  Purchase #3 $65.31   10.416%   $72.1127   $72.11   $72.10   $72.10  
  Purchase #4 $247.66   5.104%   $260.3006   $260.30   $260.30   $260.30  
  Purchase #5 $9.80   11.673%   $10.944   $10.94   $10.95   $10.90  
  Purchase #6 $185.58   11.275%   $206.5041   $206.50   $206.50   $206.50  
  Purchase #7 $197.81   4.214%   $206.1457   $206.15   $206.15   $206.10  
  7 purchase totals = $1,021.31       $1,102.8571   $1,102.85   $1,102.85   $1,102.80