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 $86.50   11.208%   $96.1949   $96.19   $96.20   $96.20  
  Purchase #2 $173.47   10.221%   $191.2004   $191.20   $191.20   $191.20  
  Purchase #3 $177.41   5.234%   $186.6956   $186.70   $186.70   $186.70  
  Purchase #4 $97.76   12.535%   $110.0142   $110.01   $110.00   $110.00  
  Purchase #5 $94.55   3.867%   $98.2062   $98.21   $98.20   $98.20  
  Purchase #6 $110.55   7.156%   $118.461   $118.46   $118.45   $118.50  
  Purchase #7 $13.94   4.178%   $14.5224   $14.52   $14.50   $14.50  
  7 purchase totals = $754.18       $815.2947   $815.29   $815.25   $815.30