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 $89.27   7.155%   $95.6573   $95.66   $95.65   $95.70  
  Purchase #2 $144.77   12.285%   $162.555   $162.56   $162.55   $162.60  
  Purchase #3 $23.42   10.503%   $25.8798   $25.88   $25.90   $25.90  
  Purchase #4 $241.37   13.349%   $273.5905   $273.59   $273.60   $273.60  
  Purchase #5 $241.76   9.273%   $264.1784   $264.18   $264.20   $264.20  
  Purchase #6 $240.54   10.444%   $265.662   $265.66   $265.65   $265.70  
  Purchase #7 $192.76   11.347%   $214.6325   $214.63   $214.65   $214.60  
  7 purchase totals = $1,173.89       $1,302.1555   $1,302.16   $1,302.20   $1,302.30