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 $89.52   6.365%   $95.2179   $95.22   $95.20   $95.20  
  Purchase #2 $58.80   13.121%   $66.5151   $66.52   $66.50   $66.50  
  Purchase #3 $207.81   3.396%   $214.8672   $214.87   $214.85   $214.90  
  Purchase #4 $83.49   5.388%   $87.9884   $87.99   $88.00   $88.00  
  Purchase #5 $29.79   7.369%   $31.9852   $31.99   $32.00   $32.00  
  Purchase #6 $171.25   7.279%   $183.7153   $183.72   $183.70   $183.70  
  Purchase #7 $192.97   11.247%   $214.6733   $214.67   $214.65   $214.70  
  7 purchase totals = $833.63       $894.9624   $894.98   $894.90   $895.00