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 $181.78   11.543%   $202.7629   $202.76   $202.75   $202.80  
  Purchase #2 $183.37   3.129%   $189.1076   $189.11   $189.10   $189.10  
  Purchase #3 $112.25   3.568%   $116.2551   $116.26   $116.25   $116.30  
  Purchase #4 $96.96   7.411%   $104.1457   $104.15   $104.15   $104.10  
  Purchase #5 $234.86   5.310%   $247.3311   $247.33   $247.35   $247.30  
  Purchase #6 $24.61   9.365%   $26.9147   $26.91   $26.90   $26.90  
  Purchase #7 $199.85   3.347%   $206.539   $206.54   $206.55   $206.50  
  7 purchase totals = $1,033.68       $1,093.0561   $1,093.06   $1,093.05   $1,093.00