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 $214.26   10.307%   $236.3438   $236.34   $236.35   $236.30  
  Purchase #2 $231.79   5.473%   $244.4759   $244.48   $244.50   $244.50  
  Purchase #3 $93.73   9.451%   $102.5884   $102.59   $102.60   $102.60  
  Purchase #4 $109.51   10.409%   $120.9089   $120.91   $120.90   $120.90  
  Purchase #5 $223.68   10.724%   $247.6674   $247.67   $247.65   $247.70  
  Purchase #6 $68.80   5.579%   $72.6384   $72.64   $72.65   $72.60  
  Purchase #7 $39.50   9.823%   $43.3801   $43.38   $43.40   $43.40  
  7 purchase totals = $981.27       $1,068.0029   $1,068.01   $1,068.05   $1,068.00