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 $72.32   5.353%   $76.1913   $76.19   $76.20   $76.20  
  Purchase #2 $114.39   6.518%   $121.8459   $121.85   $121.85   $121.80  
  Purchase #3 $53.46   5.266%   $56.2752   $56.28   $56.30   $56.30  
  Purchase #4 $145.80   5.286%   $153.507   $153.51   $153.50   $153.50  
  Purchase #5 $237.72   4.456%   $248.3128   $248.31   $248.30   $248.30  
  Purchase #6 $46.51   11.771%   $51.9847   $51.98   $52.00   $52.00  
  Purchase #7 $221.72   7.386%   $238.0962   $238.10   $238.10   $238.10  
  7 purchase totals = $891.92       $946.2131   $946.22   $946.25   $946.20