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 $67.76   4.727%   $70.963   $70.96   $70.95   $71.00  
  Purchase #2 $135.42   11.587%   $151.1111   $151.11   $151.10   $151.10  
  Purchase #3 $184.68   5.400%   $194.6527   $194.65   $194.65   $194.70  
  Purchase #4 $119.60   4.333%   $124.7823   $124.78   $124.80   $124.80  
  Purchase #5 $237.71   6.167%   $252.3696   $252.37   $252.35   $252.40  
  Purchase #6 $214.82   12.679%   $242.057   $242.06   $242.05   $242.10  
  Purchase #7 $144.90   7.157%   $155.2705   $155.27   $155.25   $155.30  
  7 purchase totals = $1,104.89       $1,191.2062   $1,191.20   $1,191.15   $1,191.40