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 $96.55   5.460%   $101.8216   $101.82   $101.80   $101.80  
  Purchase #2 $43.26   6.322%   $45.9949   $45.99   $46.00   $46.00  
  Purchase #3 $69.54   5.731%   $73.5253   $73.53   $73.55   $73.50  
  Purchase #4 $119.63   6.539%   $127.4526   $127.45   $127.45   $127.50  
  Purchase #5 $181.47   12.227%   $203.6583   $203.66   $203.65   $203.70  
  Purchase #6 $69.48   11.730%   $77.63   $77.63   $77.65   $77.60  
  Purchase #7 $62.79   11.557%   $70.0466   $70.05   $70.05   $70.00  
  7 purchase totals = $642.72       $700.1293   $700.13   $700.15   $700.10