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 $164.33   11.112%   $182.5903   $182.59   $182.60   $182.60  
  Purchase #2 $219.53   7.722%   $236.4821   $236.48   $236.50   $236.50  
  Purchase #3 $186.35   4.688%   $195.0861   $195.09   $195.10   $195.10  
  Purchase #4 $130.28   6.324%   $138.5189   $138.52   $138.50   $138.50  
  Purchase #5 $18.82   8.610%   $20.4404   $20.44   $20.45   $20.40  
  Purchase #6 $61.98   10.527%   $68.5046   $68.50   $68.50   $68.50  
  Purchase #7 $246.28   3.830%   $255.7125   $255.71   $255.70   $255.70  
  7 purchase totals = $1,027.57       $1,097.3349   $1,097.33   $1,097.35   $1,097.30