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 $81.35   5.648%   $85.9446   $85.94   $85.95   $85.90  
  Purchase #2 $113.88   12.727%   $128.3735   $128.37   $128.35   $128.40  
  Purchase #3 $235.39   4.661%   $246.3615   $246.36   $246.35   $246.40  
  Purchase #4 $234.66   4.623%   $245.5083   $245.51   $245.50   $245.50  
  Purchase #5 $209.53   6.671%   $223.5077   $223.51   $223.50   $223.50  
  Purchase #6 $86.87   9.437%   $95.0679   $95.07   $95.05   $95.10  
  Purchase #7 $167.93   8.512%   $182.2242   $182.22   $182.20   $182.20  
  7 purchase totals = $1,129.61       $1,206.9877   $1,206.98   $1,206.90   $1,207.00