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 $65.29   11.759%   $72.9675   $72.97   $72.95   $73.00  
  Purchase #2 $69.33   7.233%   $74.3446   $74.34   $74.35   $74.30  
  Purchase #3 $85.72   11.758%   $95.799   $95.80   $95.80   $95.80  
  Purchase #4 $87.53   6.740%   $93.4295   $93.43   $93.45   $93.40  
  Purchase #5 $171.90   13.719%   $195.483   $195.48   $195.50   $195.50  
  Purchase #6 $40.31   6.185%   $42.8032   $42.80   $42.80   $42.80  
  Purchase #7 $198.61   6.280%   $211.0827   $211.08   $211.10   $211.10  
  7 purchase totals = $718.69       $785.9095   $785.90   $785.95   $785.90