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 $70.27   7.230%   $75.3505   $75.35   $75.35   $75.40  
  Purchase #2 $214.72   4.136%   $223.6008   $223.60   $223.60   $223.60  
  Purchase #3 $61.27   7.121%   $65.633   $65.63   $65.65   $65.60  
  Purchase #4 $197.59   3.787%   $205.0727   $205.07   $205.05   $205.10  
  Purchase #5 $153.91   4.242%   $160.4389   $160.44   $160.45   $160.40  
  Purchase #6 $187.58   13.703%   $213.2841   $213.28   $213.30   $213.30  
  Purchase #7 $159.49   3.295%   $164.7452   $164.75   $164.75   $164.70  
  7 purchase totals = $1,044.83       $1,108.1252   $1,108.12   $1,108.15   $1,108.10