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 $44.97   3.296%   $46.4522   $46.45   $46.45   $46.50  
  Purchase #2 $243.93   6.684%   $260.2343   $260.23   $260.25   $260.20  
  Purchase #3 $185.64   3.806%   $192.7055   $192.71   $192.70   $192.70  
  Purchase #4 $10.94   11.508%   $12.199   $12.20   $12.20   $12.20  
  Purchase #5 $222.69   8.156%   $240.8526   $240.85   $240.85   $240.90  
  Purchase #6 $230.30   7.560%   $247.7107   $247.71   $247.70   $247.70  
  Purchase #7 $236.60   4.193%   $246.5206   $246.52   $246.50   $246.50  
  7 purchase totals = $1,175.07       $1,246.6749   $1,246.67   $1,246.65   $1,246.70