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 $86.47   10.586%   $95.6237   $95.62   $95.60   $95.60  
  Purchase #2 $218.65   12.504%   $245.99   $245.99   $246.00   $246.00  
  Purchase #3 $195.57   9.367%   $213.889   $213.89   $213.90   $213.90  
  Purchase #4 $244.83   9.600%   $268.3337   $268.33   $268.35   $268.30  
  Purchase #5 $216.40   13.723%   $246.0966   $246.10   $246.10   $246.10  
  Purchase #6 $68.97   4.225%   $71.884   $71.88   $71.90   $71.90  
  Purchase #7 $41.55   12.688%   $46.8219   $46.82   $46.80   $46.80  
  7 purchase totals = $1,072.44       $1,188.6389   $1,188.63   $1,188.65   $1,188.60