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 $226.82   7.580%   $244.013   $244.01   $244.00   $244.00  
  Purchase #2 $43.46   10.472%   $48.0111   $48.01   $48.00   $48.00  
  Purchase #3 $173.88   6.611%   $185.3752   $185.38   $185.40   $185.40  
  Purchase #4 $183.94   7.860%   $198.3977   $198.40   $198.40   $198.40  
  Purchase #5 $93.56   5.475%   $98.6824   $98.68   $98.70   $98.70  
  Purchase #6 $224.87   8.485%   $243.9502   $243.95   $243.95   $244.00  
  Purchase #7 $111.38   11.378%   $124.0528   $124.05   $124.05   $124.10  
  7 purchase totals = $1,057.91       $1,142.4824   $1,142.48   $1,142.50   $1,142.60