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 $42.52   3.517%   $44.0154   $44.02   $44.00   $44.00  
  Purchase #2 $174.54   4.353%   $182.1377   $182.14   $182.15   $182.10  
  Purchase #3 $60.47   3.651%   $62.6778   $62.68   $62.70   $62.70  
  Purchase #4 $233.53   8.115%   $252.481   $252.48   $252.50   $252.50  
  Purchase #5 $132.87   9.257%   $145.1698   $145.17   $145.15   $145.20  
  Purchase #6 $216.48   12.635%   $243.8322   $243.83   $243.85   $243.80  
  Purchase #7 $204.86   5.408%   $215.9388   $215.94   $215.95   $215.90  
  7 purchase totals = $1,065.27       $1,146.2527   $1,146.26   $1,146.30   $1,146.20