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 $216.65   12.600%   $243.9479   $243.95   $243.95   $243.90  
  Purchase #2 $160.34   3.153%   $165.3955   $165.40   $165.40   $165.40  
  Purchase #3 $96.92   4.125%   $100.918   $100.92   $100.90   $100.90  
  Purchase #4 $5.79   8.309%   $6.2711   $6.27   $6.25   $6.30  
  Purchase #5 $113.45   6.136%   $120.4113   $120.41   $120.40   $120.40  
  Purchase #6 $131.35   13.528%   $149.119   $149.12   $149.10   $149.10  
  Purchase #7 $228.74   4.789%   $239.6944   $239.69   $239.70   $239.70  
  7 purchase totals = $953.24       $1,025.7572   $1,025.76   $1,025.70   $1,025.70