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 $214.32   7.590%   $230.5869   $230.59   $230.60   $230.60  
  Purchase #2 $87.76   10.474%   $96.952   $96.95   $96.95   $97.00  
  Purchase #3 $135.55   12.462%   $152.4422   $152.44   $152.45   $152.40  
  Purchase #4 $147.94   13.275%   $167.579   $167.58   $167.60   $167.60  
  Purchase #5 $175.94   9.238%   $192.1933   $192.19   $192.20   $192.20  
  Purchase #6 $161.66   5.501%   $170.5529   $170.55   $170.55   $170.60  
  Purchase #7 $22.38   12.818%   $25.2487   $25.25   $25.25   $25.20  
  7 purchase totals = $945.55       $1,035.5550   $1,035.55   $1,035.60   $1,035.60