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 $61.64   5.762%   $65.1917   $65.19   $65.20   $65.20  
  Purchase #2 $127.75   4.173%   $133.081   $133.08   $133.10   $133.10  
  Purchase #3 $125.94   8.232%   $136.3074   $136.31   $136.30   $136.30  
  Purchase #4 $67.57   9.745%   $74.1547   $74.15   $74.15   $74.20  
  Purchase #5 $205.95   4.269%   $214.742   $214.74   $214.75   $214.70  
  Purchase #6 $194.51   4.303%   $202.8798   $202.88   $202.90   $202.90  
  Purchase #7 $177.67   4.190%   $185.1144   $185.11   $185.10   $185.10  
  7 purchase totals = $961.03       $1,011.4710   $1,011.46   $1,011.50   $1,011.50