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 $95.53   11.254%   $106.2809   $106.28   $106.30   $106.30  
  Purchase #2 $67.74   7.254%   $72.6539   $72.65   $72.65   $72.70  
  Purchase #3 $104.61   9.662%   $114.7174   $114.72   $114.70   $114.70  
  Purchase #4 $86.85   10.334%   $95.8251   $95.83   $95.85   $95.80  
  Purchase #5 $102.98   11.533%   $114.8567   $114.86   $114.85   $114.90  
  Purchase #6 $59.97   12.743%   $67.612   $67.61   $67.60   $67.60  
  Purchase #7 $203.99   3.290%   $210.7013   $210.70   $210.70   $210.70  
  7 purchase totals = $721.67       $782.6473   $782.65   $782.65   $782.70