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 $84.89   10.373%   $93.6956   $93.70   $93.70   $93.70  
  Purchase #2 $5.67   8.722%   $6.1645   $6.16   $6.15   $6.20  
  Purchase #3 $213.40   4.700%   $223.4298   $223.43   $223.45   $223.40  
  Purchase #4 $243.29   3.380%   $251.5132   $251.51   $251.50   $251.50  
  Purchase #5 $56.89   8.575%   $61.7683   $61.77   $61.75   $61.80  
  Purchase #6 $108.49   9.269%   $118.5459   $118.55   $118.55   $118.50  
  Purchase #7 $185.33   13.781%   $210.8703   $210.87   $210.85   $210.90  
  7 purchase totals = $897.96       $965.9876   $965.99   $965.95   $966.00