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 $71.51   6.546%   $76.191   $76.19   $76.20   $76.20  
  Purchase #2 $224.64   13.157%   $254.1959   $254.20   $254.20   $254.20  
  Purchase #3 $62.37   4.405%   $65.1174   $65.12   $65.10   $65.10  
  Purchase #4 $119.52   7.224%   $128.1541   $128.15   $128.15   $128.20  
  Purchase #5 $177.47   13.620%   $201.6414   $201.64   $201.65   $201.60  
  Purchase #6 $107.83   9.839%   $118.4394   $118.44   $118.45   $118.40  
  Purchase #7 $60.47   8.269%   $65.4703   $65.47   $65.45   $65.50  
  7 purchase totals = $823.81       $909.2095   $909.21   $909.20   $909.20