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 $71.84   5.250%   $75.6116   $75.61   $75.60   $75.60  
  Purchase #2 $206.69   11.113%   $229.6595   $229.66   $229.65   $229.70  
  Purchase #3 $109.85   11.730%   $122.7354   $122.74   $122.75   $122.70  
  Purchase #4 $243.72   6.585%   $259.769   $259.77   $259.75   $259.80  
  Purchase #5 $244.57   5.226%   $257.3512   $257.35   $257.35   $257.40  
  Purchase #6 $41.80   4.626%   $43.7337   $43.73   $43.75   $43.70  
  Purchase #7 $232.80   10.244%   $256.648   $256.65   $256.65   $256.60  
  7 purchase totals = $1,151.27       $1,245.5084   $1,245.51   $1,245.50   $1,245.50