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 $162.54   8.688%   $176.6615   $176.66   $176.65   $176.70  
  Purchase #2 $215.76   6.440%   $229.6549   $229.65   $229.65   $229.70  
  Purchase #3 $166.96   10.521%   $184.5259   $184.53   $184.55   $184.50  
  Purchase #4 $217.75   8.620%   $236.5201   $236.52   $236.50   $236.50  
  Purchase #5 $162.42   11.577%   $181.2234   $181.22   $181.20   $181.20  
  Purchase #6 $196.84   5.515%   $207.6957   $207.70   $207.70   $207.70  
  Purchase #7 $219.57   7.811%   $236.7206   $236.72   $236.70   $236.70  
  7 purchase totals = $1,341.84       $1,453.0021   $1,453.00   $1,452.95   $1,453.00