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 $211.33   13.678%   $240.2357   $240.24   $240.25   $240.20  
  Purchase #2 $248.36   7.628%   $267.3049   $267.30   $267.30   $267.30  
  Purchase #3 $167.33   9.828%   $183.7752   $183.78   $183.80   $183.80  
  Purchase #4 $57.49   7.837%   $61.9955   $62.00   $62.00   $62.00  
  Purchase #5 $83.35   4.727%   $87.29   $87.29   $87.30   $87.30  
  Purchase #6 $122.28   12.457%   $137.5124   $137.51   $137.50   $137.50  
  Purchase #7 $160.29   13.165%   $181.3922   $181.39   $181.40   $181.40  
  7 purchase totals = $1,050.43       $1,159.5059   $1,159.51   $1,159.55   $1,159.50