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 $186.64   7.506%   $200.6492   $200.65   $200.65   $200.60  
  Purchase #2 $187.79   7.803%   $202.4433   $202.44   $202.45   $202.40  
  Purchase #3 $171.63   6.474%   $182.7413   $182.74   $182.75   $182.70  
  Purchase #4 $145.53   7.219%   $156.0358   $156.04   $156.05   $156.00  
  Purchase #5 $140.61   6.209%   $149.3405   $149.34   $149.35   $149.30  
  Purchase #6 $233.33   3.844%   $242.2992   $242.30   $242.30   $242.30  
  Purchase #7 $89.95   10.677%   $99.554   $99.55   $99.55   $99.60  
  7 purchase totals = $1,155.48       $1,233.0633   $1,233.06   $1,233.10   $1,232.90