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 $214.75   5.706%   $227.0036   $227.00   $227.00   $227.00  
  Purchase #2 $248.34   13.700%   $282.3626   $282.36   $282.35   $282.40  
  Purchase #3 $15.99   10.491%   $17.6675   $17.67   $17.65   $17.70  
  Purchase #4 $223.78   13.359%   $253.6748   $253.67   $253.65   $253.70  
  Purchase #5 $201.34   9.179%   $219.821   $219.82   $219.80   $219.80  
  Purchase #6 $95.36   8.467%   $103.4341   $103.43   $103.45   $103.40  
  Purchase #7 $47.59   3.577%   $49.2923   $49.29   $49.30   $49.30  
  7 purchase totals = $1,047.15       $1,153.2559   $1,153.24   $1,153.20   $1,153.30