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 $195.96   9.380%   $214.341   $214.34   $214.35   $214.30  
  Purchase #2 $217.27   8.265%   $235.2274   $235.23   $235.25   $235.20  
  Purchase #3 $75.85   7.378%   $81.4462   $81.45   $81.45   $81.40  
  Purchase #4 $207.62   10.675%   $229.7834   $229.78   $229.80   $229.80  
  Purchase #5 $190.92   6.603%   $203.5264   $203.53   $203.55   $203.50  
  Purchase #6 $210.50   11.806%   $235.3516   $235.35   $235.35   $235.40  
  Purchase #7 $182.64   7.645%   $196.6028   $196.60   $196.60   $196.60  
  7 purchase totals = $1,280.76       $1,396.2788   $1,396.28   $1,396.35   $1,396.20