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 $120.90   4.140%   $125.9053   $125.91   $125.90   $125.90  
  Purchase #2 $228.86   6.447%   $243.6146   $243.61   $243.60   $243.60  
  Purchase #3 $169.99   6.850%   $181.6343   $181.63   $181.65   $181.60  
  Purchase #4 $245.30   12.346%   $275.5847   $275.58   $275.60   $275.60  
  Purchase #5 $148.86   6.390%   $158.3722   $158.37   $158.35   $158.40  
  Purchase #6 $238.60   6.337%   $253.7201   $253.72   $253.70   $253.70  
  Purchase #7 $94.34   13.667%   $107.2334   $107.23   $107.25   $107.20  
  7 purchase totals = $1,246.85       $1,346.0646   $1,346.05   $1,346.05   $1,346.00