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 $119.85   6.342%   $127.4509   $127.45   $127.45   $127.50  
  Purchase #2 $60.93   13.823%   $69.3524   $69.35   $69.35   $69.40  
  Purchase #3 $228.52   10.651%   $252.8597   $252.86   $252.85   $252.90  
  Purchase #4 $202.74   3.727%   $210.2961   $210.30   $210.30   $210.30  
  Purchase #5 $180.83   4.340%   $188.678   $188.68   $188.70   $188.70  
  Purchase #6 $209.37   12.388%   $235.3068   $235.31   $235.30   $235.30  
  Purchase #7 $33.71   4.852%   $35.3456   $35.35   $35.35   $35.30  
  7 purchase totals = $1,035.95       $1,119.2895   $1,119.30   $1,119.30   $1,119.40