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 $217.96   4.767%   $228.3502   $228.35   $228.35   $228.40  
  Purchase #2 $58.79   8.535%   $63.8077   $63.81   $63.80   $63.80  
  Purchase #3 $163.64   6.400%   $174.113   $174.11   $174.10   $174.10  
  Purchase #4 $232.98   7.695%   $250.9078   $250.91   $250.90   $250.90  
  Purchase #5 $238.90   10.321%   $263.5569   $263.56   $263.55   $263.60  
  Purchase #6 $247.36   10.405%   $273.0978   $273.10   $273.10   $273.10  
  Purchase #7 $199.44   3.143%   $205.7084   $205.71   $205.70   $205.70  
  7 purchase totals = $1,359.07       $1,459.5418   $1,459.55   $1,459.50   $1,459.60