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 $194.37   3.407%   $200.9922   $200.99   $201.00   $201.00  
  Purchase #2 $84.63   13.173%   $95.7783   $95.78   $95.80   $95.80  
  Purchase #3 $168.75   6.828%   $180.2723   $180.27   $180.25   $180.30  
  Purchase #4 $57.68   3.170%   $59.5085   $59.51   $59.50   $59.50  
  Purchase #5 $110.55   10.794%   $122.4828   $122.48   $122.50   $122.50  
  Purchase #6 $128.90   13.121%   $145.813   $145.81   $145.80   $145.80  
  Purchase #7 $224.72   8.114%   $242.9538   $242.95   $242.95   $243.00  
  7 purchase totals = $969.60       $1,047.8009   $1,047.79   $1,047.80   $1,047.90