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 $185.32   4.692%   $194.0152   $194.02   $194.00   $194.00  
  Purchase #2 $113.70   4.627%   $118.9609   $118.96   $118.95   $119.00  
  Purchase #3 $131.80   5.532%   $139.0912   $139.09   $139.10   $139.10  
  Purchase #4 $32.93   4.137%   $34.2923   $34.29   $34.30   $34.30  
  Purchase #5 $93.27   8.104%   $100.8286   $100.83   $100.85   $100.80  
  Purchase #6 $117.99   4.418%   $123.2028   $123.20   $123.20   $123.20  
  Purchase #7 $17.39   12.873%   $19.6286   $19.63   $19.65   $19.60  
  7 purchase totals = $692.40       $730.0196   $730.02   $730.05   $730.00