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 $85.99   12.656%   $96.8729   $96.87   $96.85   $96.90  
  Purchase #2 $230.82   9.813%   $253.4704   $253.47   $253.45   $253.50  
  Purchase #3 $94.29   13.523%   $107.0408   $107.04   $107.05   $107.00  
  Purchase #4 $55.70   12.842%   $62.853   $62.85   $62.85   $62.90  
  Purchase #5 $122.62   11.758%   $137.0377   $137.04   $137.05   $137.00  
  Purchase #6 $174.32   7.364%   $187.1569   $187.16   $187.15   $187.20  
  Purchase #7 $184.29   10.602%   $203.8284   $203.83   $203.85   $203.80  
  7 purchase totals = $948.03       $1,048.2601   $1,048.26   $1,048.25   $1,048.30