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 $193.76   6.703%   $206.7477   $206.75   $206.75   $206.70  
  Purchase #2 $240.85   10.805%   $266.8738   $266.87   $266.85   $266.90  
  Purchase #3 $90.60   9.751%   $99.4344   $99.43   $99.45   $99.40  
  Purchase #4 $93.93   11.710%   $104.9292   $104.93   $104.95   $104.90  
  Purchase #5 $182.53   6.742%   $194.8362   $194.84   $194.85   $194.80  
  Purchase #6 $236.30   5.280%   $248.7766   $248.78   $248.80   $248.80  
  Purchase #7 $130.79   7.747%   $140.9223   $140.92   $140.90   $140.90  
  7 purchase totals = $1,168.76       $1,262.5202   $1,262.52   $1,262.55   $1,262.40