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 $213.92   9.846%   $234.9826   $234.98   $235.00   $235.00  
  Purchase #2 $99.52   5.752%   $105.2444   $105.24   $105.25   $105.20  
  Purchase #3 $160.39   13.481%   $182.0122   $182.01   $182.00   $182.00  
  Purchase #4 $80.67   6.623%   $86.0128   $86.01   $86.00   $86.00  
  Purchase #5 $184.53   3.766%   $191.4794   $191.48   $191.50   $191.50  
  Purchase #6 $237.44   3.625%   $246.0472   $246.05   $246.05   $246.00  
  Purchase #7 $13.36   6.782%   $14.2661   $14.27   $14.25   $14.30  
  7 purchase totals = $989.83       $1,060.0447   $1,060.04   $1,060.05   $1,060.00