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 $243.83   6.851%   $260.5348   $260.53   $260.55   $260.50  
  Purchase #2 $243.39   3.559%   $252.0523   $252.05   $252.05   $252.10  
  Purchase #3 $213.61   5.694%   $225.773   $225.77   $225.75   $225.80  
  Purchase #4 $103.41   5.760%   $109.3664   $109.37   $109.35   $109.40  
  Purchase #5 $98.42   4.490%   $102.8391   $102.84   $102.85   $102.80  
  Purchase #6 $34.98   5.290%   $36.8304   $36.83   $36.85   $36.80  
  Purchase #7 $26.28   4.733%   $27.5238   $27.52   $27.50   $27.50  
  7 purchase totals = $963.92       $1,014.9198   $1,014.91   $1,014.90   $1,014.90