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 $141.26   7.568%   $151.9506   $151.95   $151.95   $152.00  
  Purchase #2 $13.56   10.119%   $14.9321   $14.93   $14.95   $14.90  
  Purchase #3 $241.99   9.526%   $265.042   $265.04   $265.05   $265.00  
  Purchase #4 $23.75   6.778%   $25.3598   $25.36   $25.35   $25.40  
  Purchase #5 $44.30   12.510%   $49.8419   $49.84   $49.85   $49.80  
  Purchase #6 $230.34   6.629%   $245.6092   $245.61   $245.60   $245.60  
  Purchase #7 $35.57   3.822%   $36.9295   $36.93   $36.95   $36.90  
  7 purchase totals = $730.77       $789.6651   $789.66   $789.70   $789.60