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 $124.36   13.787%   $141.5055   $141.51   $141.50   $141.50  
  Purchase #2 $161.36   12.445%   $181.4413   $181.44   $181.45   $181.40  
  Purchase #3 $231.66   9.403%   $253.443   $253.44   $253.45   $253.40  
  Purchase #4 $147.80   9.106%   $161.2587   $161.26   $161.25   $161.30  
  Purchase #5 $192.52   3.404%   $199.0734   $199.07   $199.05   $199.10  
  Purchase #6 $43.53   11.380%   $48.4837   $48.48   $48.50   $48.50  
  Purchase #7 $146.89   8.352%   $159.1583   $159.16   $159.15   $159.20  
  7 purchase totals = $1,048.12       $1,144.3639   $1,144.36   $1,144.35   $1,144.40