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 $32.48   4.455%   $33.927   $33.93   $33.95   $33.90  
  Purchase #2 $225.64   6.148%   $239.5123   $239.51   $239.50   $239.50  
  Purchase #3 $141.85   7.444%   $152.4093   $152.41   $152.40   $152.40  
  Purchase #4 $177.50   6.859%   $189.6747   $189.67   $189.65   $189.70  
  Purchase #5 $170.66   10.313%   $188.2602   $188.26   $188.25   $188.30  
  Purchase #6 $80.74   4.622%   $84.4718   $84.47   $84.45   $84.50  
  Purchase #7 $195.38   7.646%   $210.3188   $210.32   $210.30   $210.30  
  7 purchase totals = $1,024.25       $1,098.5741   $1,098.57   $1,098.50   $1,098.60