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 $207.78   13.565%   $235.9654   $235.97   $235.95   $236.00  
  Purchase #2 $106.69   3.750%   $110.6909   $110.69   $110.70   $110.70  
  Purchase #3 $169.40   6.489%   $180.3924   $180.39   $180.40   $180.40  
  Purchase #4 $238.88   7.782%   $257.4696   $257.47   $257.45   $257.50  
  Purchase #5 $61.40   6.172%   $65.1896   $65.19   $65.20   $65.20  
  Purchase #6 $109.39   5.272%   $115.157   $115.16   $115.15   $115.20  
  Purchase #7 $87.42   12.631%   $98.462   $98.46   $98.45   $98.50  
  7 purchase totals = $980.96       $1,063.3269   $1,063.33   $1,063.30   $1,063.50