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 $193.92   10.667%   $214.6054   $214.61   $214.60   $214.60  
  Purchase #2 $85.71   11.265%   $95.3652   $95.37   $95.35   $95.40  
  Purchase #3 $10.71   13.377%   $12.1427   $12.14   $12.15   $12.10  
  Purchase #4 $192.95   6.145%   $204.8068   $204.81   $204.80   $204.80  
  Purchase #5 $189.37   12.580%   $213.1927   $213.19   $213.20   $213.20  
  Purchase #6 $98.58   12.151%   $110.5585   $110.56   $110.55   $110.60  
  Purchase #7 $140.64   11.266%   $156.4845   $156.48   $156.50   $156.50  
  7 purchase totals = $911.88       $1,007.1558   $1,007.16   $1,007.15   $1,007.20