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 $88.69   9.296%   $96.9346   $96.93   $96.95   $96.90  
  Purchase #2 $200.32   11.324%   $223.0042   $223.00   $223.00   $223.00  
  Purchase #3 $61.64   4.728%   $64.5543   $64.55   $64.55   $64.60  
  Purchase #4 $26.46   4.778%   $27.7243   $27.72   $27.70   $27.70  
  Purchase #5 $122.36   10.510%   $135.22   $135.22   $135.20   $135.20  
  Purchase #6 $199.70   9.725%   $219.1208   $219.12   $219.10   $219.10  
  Purchase #7 $155.28   7.547%   $166.999   $167.00   $167.00   $167.00  
  7 purchase totals = $854.45       $933.5572   $933.54   $933.50   $933.50