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 $197.50   8.279%   $213.851   $213.85   $213.85   $213.90  
  Purchase #2 $91.53   7.722%   $98.5979   $98.60   $98.60   $98.60  
  Purchase #3 $126.75   13.209%   $143.4924   $143.49   $143.50   $143.50  
  Purchase #4 $32.92   7.823%   $35.4953   $35.50   $35.50   $35.50  
  Purchase #5 $88.42   9.492%   $96.8128   $96.81   $96.80   $96.80  
  Purchase #6 $189.56   5.125%   $199.275   $199.28   $199.30   $199.30  
  Purchase #7 $220.61   11.270%   $245.4727   $245.47   $245.45   $245.50  
  7 purchase totals = $947.29       $1,032.9971   $1,033.00   $1,033.00   $1,033.10