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 $223.38   12.853%   $252.091   $252.09   $252.10   $252.10  
  Purchase #2 $180.95   10.838%   $200.5614   $200.56   $200.55   $200.60  
  Purchase #3 $88.26   7.419%   $94.808   $94.81   $94.80   $94.80  
  Purchase #4 $113.48   9.731%   $124.5227   $124.52   $124.50   $124.50  
  Purchase #5 $168.47   3.752%   $174.791   $174.79   $174.80   $174.80  
  Purchase #6 $83.44   3.865%   $86.665   $86.67   $86.65   $86.70  
  Purchase #7 $75.90   6.529%   $80.8555   $80.86   $80.85   $80.90  
  7 purchase totals = $933.88       $1,014.2946   $1,014.30   $1,014.25   $1,014.40