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 $181.93   11.583%   $203.003   $203.00   $203.00   $203.00  
  Purchase #2 $150.62   10.407%   $166.295   $166.30   $166.30   $166.30  
  Purchase #3 $139.81   5.596%   $147.6338   $147.63   $147.65   $147.60  
  Purchase #4 $14.36   12.612%   $16.1711   $16.17   $16.15   $16.20  
  Purchase #5 $90.93   8.350%   $98.5227   $98.52   $98.50   $98.50  
  Purchase #6 $24.79   5.333%   $26.1121   $26.11   $26.10   $26.10  
  Purchase #7 $87.60   9.580%   $95.9921   $95.99   $96.00   $96.00  
  7 purchase totals = $690.04       $753.7298   $753.72   $753.70   $753.70