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 $100.47   9.458%   $109.9725   $109.97   $109.95   $110.00  
  Purchase #2 $132.94   8.520%   $144.2665   $144.27   $144.25   $144.30  
  Purchase #3 $199.95   3.473%   $206.8943   $206.89   $206.90   $206.90  
  Purchase #4 $219.94   12.253%   $246.8892   $246.89   $246.90   $246.90  
  Purchase #5 $143.43   4.221%   $149.4842   $149.48   $149.50   $149.50  
  Purchase #6 $24.96   7.513%   $26.8352   $26.84   $26.85   $26.80  
  Purchase #7 $248.77   3.629%   $257.7979   $257.80   $257.80   $257.80  
  7 purchase totals = $1,070.46       $1,142.1398   $1,142.14   $1,142.15   $1,142.20