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 $180.85   6.525%   $192.6505   $192.65   $192.65   $192.70  
  Purchase #2 $162.65   7.603%   $175.0163   $175.02   $175.00   $175.00  
  Purchase #3 $151.55   5.690%   $160.1732   $160.17   $160.15   $160.20  
  Purchase #4 $168.52   4.284%   $175.7394   $175.74   $175.75   $175.70  
  Purchase #5 $65.68   11.131%   $72.9908   $72.99   $73.00   $73.00  
  Purchase #6 $229.32   4.284%   $239.1441   $239.14   $239.15   $239.10  
  Purchase #7 $170.44   5.186%   $179.279   $179.28   $179.30   $179.30  
  7 purchase totals = $1,129.01       $1,194.9933   $1,194.99   $1,195.00   $1,195.00