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 $86.81   9.818%   $95.333   $95.33   $95.35   $95.30  
  Purchase #2 $156.55   10.430%   $172.8782   $172.88   $172.90   $172.90  
  Purchase #3 $180.94   11.647%   $202.0141   $202.01   $202.00   $202.00  
  Purchase #4 $30.30   13.109%   $34.272   $34.27   $34.25   $34.30  
  Purchase #5 $246.98   6.870%   $263.9475   $263.95   $263.95   $263.90  
  Purchase #6 $148.94   5.780%   $157.5487   $157.55   $157.55   $157.50  
  Purchase #7 $211.87   9.719%   $232.4616   $232.46   $232.45   $232.50  
  7 purchase totals = $1,062.39       $1,158.4551   $1,158.45   $1,158.45   $1,158.40