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 $208.50   11.783%   $233.0676   $233.07   $233.05   $233.10  
  Purchase #2 $180.59   9.462%   $197.6774   $197.68   $197.70   $197.70  
  Purchase #3 $78.76   12.578%   $88.6664   $88.67   $88.65   $88.70  
  Purchase #4 $197.56   9.750%   $216.8221   $216.82   $216.80   $216.80  
  Purchase #5 $154.72   3.273%   $159.784   $159.78   $159.80   $159.80  
  Purchase #6 $96.94   7.244%   $103.9623   $103.96   $103.95   $104.00  
  Purchase #7 $175.83   9.218%   $192.038   $192.04   $192.05   $192.00  
  7 purchase totals = $1,092.90       $1,192.0178   $1,192.02   $1,192.00   $1,192.10