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 $192.75   10.736%   $213.4436   $213.44   $213.45   $213.40  
  Purchase #2 $232.93   3.697%   $241.5414   $241.54   $241.55   $241.50  
  Purchase #3 $198.72   6.787%   $212.2071   $212.21   $212.20   $212.20  
  Purchase #4 $172.64   8.776%   $187.7909   $187.79   $187.80   $187.80  
  Purchase #5 $189.40   3.217%   $195.493   $195.49   $195.50   $195.50  
  Purchase #6 $87.90   9.688%   $96.4158   $96.42   $96.40   $96.40  
  Purchase #7 $8.28   6.627%   $8.8287   $8.83   $8.85   $8.80  
  7 purchase totals = $1,082.62       $1,155.7205   $1,155.72   $1,155.75   $1,155.60