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 $173.39   5.446%   $182.8328   $182.83   $182.85   $182.80  
  Purchase #2 $54.92   6.314%   $58.3876   $58.39   $58.40   $58.40  
  Purchase #3 $219.56   4.626%   $229.7168   $229.72   $229.70   $229.70  
  Purchase #4 $158.90   10.757%   $175.9929   $175.99   $176.00   $176.00  
  Purchase #5 $80.28   6.585%   $85.5664   $85.57   $85.55   $85.60  
  Purchase #6 $121.43   13.792%   $138.1776   $138.18   $138.20   $138.20  
  Purchase #7 $186.58   3.334%   $192.8006   $192.80   $192.80   $192.80  
  7 purchase totals = $995.06       $1,063.4747   $1,063.48   $1,063.50   $1,063.50