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 $62.26   11.559%   $69.4566   $69.46   $69.45   $69.50  
  Purchase #2 $227.53   4.435%   $237.621   $237.62   $237.60   $237.60  
  Purchase #3 $117.45   9.221%   $128.2801   $128.28   $128.30   $128.30  
  Purchase #4 $160.70   11.645%   $179.4135   $179.41   $179.40   $179.40  
  Purchase #5 $213.25   4.810%   $223.5073   $223.51   $223.50   $223.50  
  Purchase #6 $143.80   13.748%   $163.5696   $163.57   $163.55   $163.60  
  Purchase #7 $61.68   7.356%   $66.2172   $66.22   $66.20   $66.20  
  7 purchase totals = $986.67       $1,068.0653   $1,068.07   $1,068.00   $1,068.10