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 $46.62   6.558%   $49.6773   $49.68   $49.70   $49.70  
  Purchase #2 $22.94   5.590%   $24.2223   $24.22   $24.20   $24.20  
  Purchase #3 $162.28   7.585%   $174.5889   $174.59   $174.60   $174.60  
  Purchase #4 $199.35   13.856%   $226.9719   $226.97   $226.95   $227.00  
  Purchase #5 $199.56   11.639%   $222.7868   $222.79   $222.80   $222.80  
  Purchase #6 $195.58   13.549%   $222.0791   $222.08   $222.10   $222.10  
  Purchase #7 $247.54   11.230%   $275.3387   $275.34   $275.35   $275.30  
  7 purchase totals = $1,073.87       $1,195.6650   $1,195.67   $1,195.70   $1,195.70