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 $109.49   6.605%   $116.7218   $116.72   $116.70   $116.70  
  Purchase #2 $214.71   5.541%   $226.6071   $226.61   $226.60   $226.60  
  Purchase #3 $161.93   3.201%   $167.1134   $167.11   $167.10   $167.10  
  Purchase #4 $67.91   9.237%   $74.1828   $74.18   $74.20   $74.20  
  Purchase #5 $83.49   5.730%   $88.274   $88.27   $88.25   $88.30  
  Purchase #6 $139.33   12.374%   $156.5707   $156.57   $156.55   $156.60  
  Purchase #7 $248.95   6.760%   $265.779   $265.78   $265.80   $265.80  
  7 purchase totals = $1,025.81       $1,095.2488   $1,095.24   $1,095.20   $1,095.30