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 $206.27   8.754%   $224.3269   $224.33   $224.35   $224.30  
  Purchase #2 $217.76   7.671%   $234.4644   $234.46   $234.45   $234.50  
  Purchase #3 $84.29   4.589%   $88.1581   $88.16   $88.15   $88.20  
  Purchase #4 $201.26   6.581%   $214.5049   $214.50   $214.50   $214.50  
  Purchase #5 $153.45   3.529%   $158.8653   $158.87   $158.85   $158.90  
  Purchase #6 $80.91   12.804%   $91.2697   $91.27   $91.25   $91.30  
  Purchase #7 $190.95   10.365%   $210.742   $210.74   $210.75   $210.70  
  7 purchase totals = $1,134.89       $1,222.3313   $1,222.33   $1,222.30   $1,222.40