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 $215.80   8.717%   $234.6113   $234.61   $234.60   $234.60  
  Purchase #2 $175.37   13.677%   $199.3554   $199.36   $199.35   $199.40  
  Purchase #3 $181.58   6.408%   $193.2156   $193.22   $193.20   $193.20  
  Purchase #4 $52.73   11.711%   $58.9052   $58.91   $58.90   $58.90  
  Purchase #5 $198.92   4.366%   $207.6048   $207.60   $207.60   $207.60  
  Purchase #6 $231.67   9.459%   $253.5837   $253.58   $253.60   $253.60  
  Purchase #7 $55.31   13.428%   $62.737   $62.74   $62.75   $62.70  
  7 purchase totals = $1,111.38       $1,210.0130   $1,210.02   $1,210.00   $1,210.00