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 $12.76   9.768%   $14.0064   $14.01   $14.00   $14.00  
  Purchase #2 $107.97   6.767%   $115.2763   $115.28   $115.30   $115.30  
  Purchase #3 $223.65   4.756%   $234.2868   $234.29   $234.30   $234.30  
  Purchase #4 $52.52   13.286%   $59.4978   $59.50   $59.50   $59.50  
  Purchase #5 $116.39   12.515%   $130.9562   $130.96   $130.95   $131.00  
  Purchase #6 $90.82   6.412%   $96.6434   $96.64   $96.65   $96.60  
  Purchase #7 $232.82   5.367%   $245.3154   $245.32   $245.30   $245.30  
  7 purchase totals = $836.93       $895.9823   $896.00   $896.00   $896.00