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 $88.52   7.299%   $94.9811   $94.98   $95.00   $95.00  
  Purchase #2 $131.74   5.430%   $138.8935   $138.89   $138.90   $138.90  
  Purchase #3 $145.30   8.868%   $158.1852   $158.19   $158.20   $158.20  
  Purchase #4 $227.27   3.577%   $235.3994   $235.40   $235.40   $235.40  
  Purchase #5 $189.94   4.552%   $198.5861   $198.59   $198.60   $198.60  
  Purchase #6 $250.61   7.587%   $269.6238   $269.62   $269.60   $269.60  
  Purchase #7 $161.43   10.682%   $178.674   $178.67   $178.65   $178.70  
  7 purchase totals = $1,194.81       $1,274.3431   $1,274.34   $1,274.35   $1,274.40