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 $195.58   7.554%   $210.3541   $210.35   $210.35   $210.40  
  Purchase #2 $146.46   10.517%   $161.8632   $161.86   $161.85   $161.90  
  Purchase #3 $110.72   9.498%   $121.2362   $121.24   $121.25   $121.20  
  Purchase #4 $90.40   6.716%   $96.4713   $96.47   $96.45   $96.50  
  Purchase #5 $35.76   10.510%   $39.5184   $39.52   $39.50   $39.50  
  Purchase #6 $186.63   13.578%   $211.9706   $211.97   $211.95   $212.00  
  Purchase #7 $211.59   7.125%   $226.6658   $226.67   $226.65   $226.70  
  7 purchase totals = $977.14       $1,068.0796   $1,068.08   $1,068.00   $1,068.20