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 $65.64   13.685%   $74.6228   $74.62   $74.60   $74.60  
  Purchase #2 $153.85   5.847%   $162.8456   $162.85   $162.85   $162.80  
  Purchase #3 $220.32   7.277%   $236.3527   $236.35   $236.35   $236.40  
  Purchase #4 $172.40   10.747%   $190.9278   $190.93   $190.95   $190.90  
  Purchase #5 $182.30   10.722%   $201.8462   $201.85   $201.85   $201.80  
  Purchase #6 $152.37   5.737%   $161.1115   $161.11   $161.10   $161.10  
  Purchase #7 $215.53   9.836%   $236.7295   $236.73   $236.75   $236.70  
  7 purchase totals = $1,162.41       $1,264.4361   $1,264.44   $1,264.45   $1,264.30