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 $57.75   8.336%   $62.564   $62.56   $62.55   $62.60  
  Purchase #2 $120.38   6.358%   $128.0338   $128.03   $128.05   $128.00  
  Purchase #3 $13.37   12.828%   $15.0851   $15.09   $15.10   $15.10  
  Purchase #4 $54.97   10.618%   $60.8067   $60.81   $60.80   $60.80  
  Purchase #5 $135.72   8.321%   $147.0133   $147.01   $147.00   $147.00  
  Purchase #6 $39.78   5.122%   $41.8175   $41.82   $41.80   $41.80  
  Purchase #7 $232.72   3.235%   $240.2485   $240.25   $240.25   $240.20  
  7 purchase totals = $654.69       $695.5689   $695.57   $695.55   $695.50