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 $84.69   12.179%   $95.0044   $95.00   $95.00   $95.00  
  Purchase #2 $134.79   13.371%   $152.8128   $152.81   $152.80   $152.80  
  Purchase #3 $49.51   8.814%   $53.8738   $53.87   $53.85   $53.90  
  Purchase #4 $148.82   3.465%   $153.9766   $153.98   $154.00   $154.00  
  Purchase #5 $121.55   4.651%   $127.2033   $127.20   $127.20   $127.20  
  Purchase #6 $60.40   9.154%   $65.929   $65.93   $65.95   $65.90  
  Purchase #7 $149.57   9.777%   $164.1935   $164.19   $164.20   $164.20  
  7 purchase totals = $749.33       $812.9934   $812.98   $813.00   $813.00