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 $59.46   4.856%   $62.3474   $62.35   $62.35   $62.30  
  Purchase #2 $244.79   5.801%   $258.9903   $258.99   $259.00   $259.00  
  Purchase #3 $132.75   9.396%   $145.2232   $145.22   $145.20   $145.20  
  Purchase #4 $29.99   5.713%   $31.7033   $31.70   $31.70   $31.70  
  Purchase #5 $230.26   6.463%   $245.1417   $245.14   $245.15   $245.10  
  Purchase #6 $150.51   4.112%   $156.699   $156.70   $156.70   $156.70  
  Purchase #7 $117.61   8.142%   $127.1858   $127.19   $127.20   $127.20  
  7 purchase totals = $965.37       $1,027.2907   $1,027.29   $1,027.30   $1,027.20