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 $206.76   9.154%   $225.6868   $225.69   $225.70   $225.70  
  Purchase #2 $148.57   3.389%   $153.605   $153.61   $153.60   $153.60  
  Purchase #3 $17.46   6.716%   $18.6326   $18.63   $18.65   $18.60  
  Purchase #4 $217.61   11.111%   $241.7886   $241.79   $241.80   $241.80  
  Purchase #5 $192.60   3.461%   $199.2659   $199.27   $199.25   $199.30  
  Purchase #6 $151.35   5.269%   $159.3246   $159.32   $159.30   $159.30  
  Purchase #7 $178.52   13.778%   $203.1165   $203.12   $203.10   $203.10  
  7 purchase totals = $1,112.87       $1,201.4200   $1,201.43   $1,201.40   $1,201.40