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 $43.86   6.860%   $46.8688   $46.87   $46.85   $46.90  
  Purchase #2 $180.99   3.123%   $186.6423   $186.64   $186.65   $186.60  
  Purchase #3 $105.99   10.192%   $116.7925   $116.79   $116.80   $116.80  
  Purchase #4 $205.67   5.425%   $216.8276   $216.83   $216.85   $216.80  
  Purchase #5 $218.83   10.801%   $242.4658   $242.47   $242.45   $242.50  
  Purchase #6 $126.82   11.180%   $140.9985   $141.00   $141.00   $141.00  
  Purchase #7 $73.48   13.483%   $83.3873   $83.39   $83.40   $83.40  
  7 purchase totals = $955.64       $1,033.9828   $1,033.99   $1,034.00   $1,034.00