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 $88.33   4.857%   $92.6202   $92.62   $92.60   $92.60  
  Purchase #2 $225.29   10.721%   $249.4433   $249.44   $249.45   $249.40  
  Purchase #3 $226.94   5.242%   $238.8362   $238.84   $238.85   $238.80  
  Purchase #4 $235.38   11.642%   $262.7829   $262.78   $262.80   $262.80  
  Purchase #5 $101.66   5.418%   $107.1679   $107.17   $107.15   $107.20  
  Purchase #6 $176.27   11.867%   $197.188   $197.19   $197.20   $197.20  
  Purchase #7 $48.83   11.151%   $54.275   $54.28   $54.30   $54.30  
  7 purchase totals = $1,102.70       $1,202.3135   $1,202.32   $1,202.35   $1,202.30