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 $88.52   7.397%   $95.0678   $95.07   $95.05   $95.10  
  Purchase #2 $187.85   5.194%   $197.6069   $197.61   $197.60   $197.60  
  Purchase #3 $126.73   5.610%   $133.8396   $133.84   $133.85   $133.80  
  Purchase #4 $238.41   5.864%   $252.3904   $252.39   $252.40   $252.40  
  Purchase #5 $214.32   10.638%   $237.1194   $237.12   $237.10   $237.10  
  Purchase #6 $204.75   13.704%   $232.8089   $232.81   $232.80   $232.80  
  Purchase #7 $98.85   13.579%   $112.2728   $112.27   $112.25   $112.30  
  7 purchase totals = $1,159.43       $1,261.1058   $1,261.11   $1,261.05   $1,261.10