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 $114.50   4.106%   $119.2014   $119.20   $119.20   $119.20  
  Purchase #2 $105.37   9.453%   $115.3306   $115.33   $115.35   $115.30  
  Purchase #3 $88.37   5.562%   $93.2851   $93.29   $93.30   $93.30  
  Purchase #4 $145.60   13.636%   $165.454   $165.45   $165.45   $165.50  
  Purchase #5 $177.82   7.187%   $190.5999   $190.60   $190.60   $190.60  
  Purchase #6 $216.63   11.435%   $241.4016   $241.40   $241.40   $241.40  
  Purchase #7 $197.63   13.756%   $224.816   $224.82   $224.80   $224.80  
  7 purchase totals = $1,045.92       $1,150.0886   $1,150.09   $1,150.10   $1,150.10