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 $73.36   3.870%   $76.199   $76.20   $76.20   $76.20  
  Purchase #2 $34.50   6.120%   $36.6114   $36.61   $36.60   $36.60  
  Purchase #3 $194.44   6.587%   $207.2478   $207.25   $207.25   $207.20  
  Purchase #4 $10.78   5.270%   $11.3481   $11.35   $11.35   $11.30  
  Purchase #5 $105.66   4.187%   $110.084   $110.08   $110.10   $110.10  
  Purchase #6 $83.27   5.281%   $87.6675   $87.67   $87.65   $87.70  
  Purchase #7 $223.34   4.559%   $233.5221   $233.52   $233.50   $233.50  
  7 purchase totals = $725.35       $762.6799   $762.68   $762.65   $762.60