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 $95.63   10.811%   $105.9686   $105.97   $105.95   $106.00  
  Purchase #2 $6.86   3.579%   $7.1055   $7.11   $7.10   $7.10  
  Purchase #3 $192.31   4.386%   $200.7447   $200.74   $200.75   $200.70  
  Purchase #4 $157.59   12.497%   $177.284   $177.28   $177.30   $177.30  
  Purchase #5 $125.59   5.658%   $132.6959   $132.70   $132.70   $132.70  
  Purchase #6 $245.35   12.385%   $275.7366   $275.74   $275.75   $275.70  
  Purchase #7 $144.48   6.380%   $153.6978   $153.70   $153.70   $153.70  
  7 purchase totals = $967.81       $1,053.2331   $1,053.24   $1,053.25   $1,053.20