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 $96.29   11.124%   $107.0013   $107.00   $107.00   $107.00  
  Purchase #2 $203.46   13.609%   $231.1489   $231.15   $231.15   $231.10  
  Purchase #3 $219.62   11.195%   $244.2065   $244.21   $244.20   $244.20  
  Purchase #4 $216.47   5.643%   $228.6854   $228.69   $228.70   $228.70  
  Purchase #5 $25.98   6.305%   $27.618   $27.62   $27.60   $27.60  
  Purchase #6 $154.98   13.735%   $176.2665   $176.27   $176.25   $176.30  
  Purchase #7 $80.63   13.656%   $91.6408   $91.64   $91.65   $91.60  
  7 purchase totals = $997.43       $1,106.5674   $1,106.58   $1,106.55   $1,106.50