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 $206.78   13.776%   $235.266   $235.27   $235.25   $235.30  
  Purchase #2 $31.57   3.259%   $32.5989   $32.60   $32.60   $32.60  
  Purchase #3 $155.64   12.515%   $175.1183   $175.12   $175.10   $175.10  
  Purchase #4 $199.78   5.607%   $210.9817   $210.98   $211.00   $211.00  
  Purchase #5 $24.38   7.331%   $26.1673   $26.17   $26.15   $26.20  
  Purchase #6 $109.61   7.706%   $118.0565   $118.06   $118.05   $118.10  
  Purchase #7 $226.75   3.149%   $233.8904   $233.89   $233.90   $233.90  
  7 purchase totals = $954.51       $1,032.0791   $1,032.09   $1,032.05   $1,032.20