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 $213.99   10.442%   $236.3348   $236.33   $236.35   $236.30  
  Purchase #2 $196.62   4.731%   $205.9221   $205.92   $205.90   $205.90  
  Purchase #3 $72.56   8.515%   $78.7385   $78.74   $78.75   $78.70  
  Purchase #4 $205.67   9.840%   $225.9079   $225.91   $225.90   $225.90  
  Purchase #5 $247.70   6.448%   $263.6717   $263.67   $263.65   $263.70  
  Purchase #6 $15.59   3.377%   $16.1165   $16.12   $16.10   $16.10  
  Purchase #7 $101.34   4.765%   $106.1689   $106.17   $106.15   $106.20  
  7 purchase totals = $1,053.47       $1,132.8604   $1,132.86   $1,132.80   $1,132.80