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 $181.81   11.244%   $202.2527   $202.25   $202.25   $202.30  
  Purchase #2 $127.46   13.174%   $144.2516   $144.25   $144.25   $144.30  
  Purchase #3 $103.50   6.470%   $110.1965   $110.20   $110.20   $110.20  
  Purchase #4 $160.86   4.308%   $167.7898   $167.79   $167.80   $167.80  
  Purchase #5 $160.99   8.393%   $174.5019   $174.50   $174.50   $174.50  
  Purchase #6 $68.43   3.770%   $71.0098   $71.01   $71.00   $71.00  
  Purchase #7 $158.86   9.851%   $174.5093   $174.51   $174.50   $174.50  
  7 purchase totals = $961.91       $1,044.5116   $1,044.51   $1,044.50   $1,044.60