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 $65.26   10.322%   $71.9961   $72.00   $72.00   $72.00  
  Purchase #2 $119.41   9.199%   $130.3945   $130.39   $130.40   $130.40  
  Purchase #3 $120.63   3.198%   $124.4877   $124.49   $124.50   $124.50  
  Purchase #4 $82.72   4.816%   $86.7038   $86.70   $86.70   $86.70  
  Purchase #5 $168.28   12.707%   $189.6633   $189.66   $189.65   $189.70  
  Purchase #6 $187.56   4.232%   $195.4975   $195.50   $195.50   $195.50  
  Purchase #7 $205.41   10.640%   $227.2656   $227.27   $227.25   $227.30  
  7 purchase totals = $949.27       $1,026.0085   $1,026.01   $1,026.00   $1,026.10