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 $93.70   8.482%   $101.6476   $101.65   $101.65   $101.60  
  Purchase #2 $72.26   5.715%   $76.3897   $76.39   $76.40   $76.40  
  Purchase #3 $153.62   9.798%   $168.6717   $168.67   $168.65   $168.70  
  Purchase #4 $68.83   13.484%   $78.111   $78.11   $78.10   $78.10  
  Purchase #5 $227.50   6.339%   $241.9212   $241.92   $241.90   $241.90  
  Purchase #6 $210.82   9.122%   $230.051   $230.05   $230.05   $230.10  
  Purchase #7 $225.85   11.155%   $251.0436   $251.04   $251.05   $251.00  
  7 purchase totals = $1,052.58       $1,147.8358   $1,147.83   $1,147.80   $1,147.80