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 $83.42   12.650%   $93.9726   $93.97   $93.95   $94.00  
  Purchase #2 $114.76   8.584%   $124.611   $124.61   $124.60   $124.60  
  Purchase #3 $223.38   9.673%   $244.9875   $244.99   $245.00   $245.00  
  Purchase #4 $185.53   9.306%   $202.7954   $202.80   $202.80   $202.80  
  Purchase #5 $210.77   7.405%   $226.3775   $226.38   $226.40   $226.40  
  Purchase #6 $48.80   9.383%   $53.3789   $53.38   $53.40   $53.40  
  Purchase #7 $49.97   9.342%   $54.6382   $54.64   $54.65   $54.60  
  7 purchase totals = $916.63       $1,000.7611   $1,000.77   $1,000.80   $1,000.80