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 $92.57   4.852%   $97.0615   $97.06   $97.05   $97.10  
  Purchase #2 $40.74   7.758%   $43.9006   $43.90   $43.90   $43.90  
  Purchase #3 $244.43   11.870%   $273.4438   $273.44   $273.45   $273.40  
  Purchase #4 $48.72   10.107%   $53.6441   $53.64   $53.65   $53.60  
  Purchase #5 $219.51   7.239%   $235.4003   $235.40   $235.40   $235.40  
  Purchase #6 $133.41   11.246%   $148.4133   $148.41   $148.40   $148.40  
  Purchase #7 $39.33   11.366%   $43.8002   $43.80   $43.80   $43.80  
  7 purchase totals = $818.71       $895.6638   $895.65   $895.65   $895.60