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 $41.49   3.732%   $43.0384   $43.04   $43.05   $43.00  
  Purchase #2 $238.62   10.628%   $263.9805   $263.98   $264.00   $264.00  
  Purchase #3 $207.76   13.655%   $236.1296   $236.13   $236.15   $236.10  
  Purchase #4 $205.85   3.831%   $213.7361   $213.74   $213.75   $213.70  
  Purchase #5 $220.34   11.717%   $246.1572   $246.16   $246.15   $246.20  
  Purchase #6 $183.69   4.661%   $192.2518   $192.25   $192.25   $192.30  
  Purchase #7 $181.88   13.200%   $205.8882   $205.89   $205.90   $205.90  
  7 purchase totals = $1,279.63       $1,401.1818   $1,401.19   $1,401.25   $1,401.20