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 $57.62   8.737%   $62.6543   $62.65   $62.65   $62.70  
  Purchase #2 $99.35   4.541%   $103.8615   $103.86   $103.85   $103.90  
  Purchase #3 $213.75   5.779%   $226.1026   $226.10   $226.10   $226.10  
  Purchase #4 $133.65   7.628%   $143.8448   $143.84   $143.85   $143.80  
  Purchase #5 $136.81   7.825%   $147.5154   $147.52   $147.50   $147.50  
  Purchase #6 $203.82   8.267%   $220.6698   $220.67   $220.65   $220.70  
  Purchase #7 $177.69   12.711%   $200.2762   $200.28   $200.30   $200.30  
  7 purchase totals = $1,022.69       $1,104.9246   $1,104.92   $1,104.90   $1,105.00