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 $227.95   7.814%   $245.762   $245.76   $245.75   $245.80  
  Purchase #2 $233.88   5.532%   $246.8182   $246.82   $246.80   $246.80  
  Purchase #3 $58.39   8.271%   $63.2194   $63.22   $63.20   $63.20  
  Purchase #4 $9.46   13.492%   $10.7363   $10.74   $10.75   $10.70  
  Purchase #5 $66.98   5.246%   $70.4938   $70.49   $70.50   $70.50  
  Purchase #6 $203.45   11.252%   $226.3422   $226.34   $226.35   $226.30  
  Purchase #7 $165.78   12.202%   $186.0085   $186.01   $186.00   $186.00  
  7 purchase totals = $965.89       $1,049.3804   $1,049.38   $1,049.35   $1,049.30