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 $201.27   6.363%   $214.0768   $214.08   $214.10   $214.10  
  Purchase #2 $49.29   11.817%   $55.1146   $55.11   $55.10   $55.10  
  Purchase #3 $95.34   9.773%   $104.6576   $104.66   $104.65   $104.70  
  Purchase #4 $186.42   13.262%   $211.143   $211.14   $211.15   $211.10  
  Purchase #5 $153.80   7.545%   $165.4042   $165.40   $165.40   $165.40  
  Purchase #6 $159.45   11.790%   $178.2492   $178.25   $178.25   $178.20  
  Purchase #7 $90.70   6.535%   $96.6272   $96.63   $96.65   $96.60  
  7 purchase totals = $936.27       $1,025.2726   $1,025.27   $1,025.30   $1,025.20