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 $178.25   9.855%   $195.8165   $195.82   $195.80   $195.80  
  Purchase #2 $8.46   13.293%   $9.5846   $9.58   $9.60   $9.60  
  Purchase #3 $13.81   6.178%   $14.6632   $14.66   $14.65   $14.70  
  Purchase #4 $114.46   5.114%   $120.3135   $120.31   $120.30   $120.30  
  Purchase #5 $128.41   3.456%   $132.8478   $132.85   $132.85   $132.80  
  Purchase #6 $178.25   13.578%   $202.4528   $202.45   $202.45   $202.50  
  Purchase #7 $103.38   7.144%   $110.7655   $110.77   $110.75   $110.80  
  7 purchase totals = $725.02       $786.4439   $786.44   $786.40   $786.50