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 $63.69   8.355%   $69.0113   $69.01   $69.00   $69.00  
  Purchase #2 $217.55   13.566%   $247.0628   $247.06   $247.05   $247.10  
  Purchase #3 $221.70   8.705%   $240.999   $241.00   $241.00   $241.00  
  Purchase #4 $166.43   9.111%   $181.5934   $181.59   $181.60   $181.60  
  Purchase #5 $112.93   4.728%   $118.2693   $118.27   $118.25   $118.30  
  Purchase #6 $139.97   9.678%   $153.5163   $153.52   $153.50   $153.50  
  Purchase #7 $74.46   12.859%   $84.0348   $84.03   $84.05   $84.00  
  7 purchase totals = $996.73       $1,094.4869   $1,094.48   $1,094.45   $1,094.50